Description of problem:
Boot up guest with virtio serial with max ports and only 15 ports were available.

Version-Release number of selected component (if applicable):
kernel-3.10.0-53.el7.x86_64
qemu-kvm-rhev-1.5.3-19.el7.x86_64
virtio-win 1.6.7-2 
How reproducible:
only once

Steps to Reproduce:
1.boot up guest with virtio serial 
  /usr/libexec/qemu-kvm -M pc -cpu host -enable-kvm -m 4G -smp 2 -name win2k8-64-nerkvm -rtc base=localtime,clock=host,driftfix=slew -uuid 816c2e3d-e84f-4de9-b919-7d1cfd226b6d -monitor stdio -drive file=win8-32.qcow3,if=none,id=drive-data-disk2,format=qcow2,cache=none,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk2,id=systemos -global PIIX4_PM.disable_s3=0 -global PIIX4_PM.disable_s4=0 -netdev tap,sndbuf=0,id=hostnet0,script=/etc/qemu-ifup,downscript=no -device e1000,netdev=hostnet0,mac=00:32:52:41:31:31,id=net1 -cdrom /usr/share/virtio-win/virtio-win-1.6.7.iso -vga cirrus -chardev socket,id=abc,path=/tmp/monitor-win8-64-scsi-73,server,nowait -mon chardev=abc,mode=readline  -device virtio-serial-pci,id=virtio-serial0,max_ports=31 -chardev socket,id=channel1,path=/tmp/helloworld1,server,nowait -device virtserialport,nr=1,chardev=channel1,name=com.redhat.rhevm.vdsm1,bus=virtio-serial0.0,id=port1 -chardev socket,id=channel2,path=/tmp/helloworld2,server,nowait -device virtserialport,nr=2,chardev=channel2,name=com.redhat.rhevm.vdsm2,bus=virtio-serial0.0,id=port2 -chardev socket,id=channel3,path=/tmp/helloworld3,server,nowait -device virtserialport,nr=3,chardev=channel3,name=com.redhat.rhevm.vdsm3,bus=virtio-serial0.0,id=port3 -chardev socket,id=channel4,path=/tmp/helloworld4,server,nowait -device virtserialport,nr=4,chardev=channel4,name=com.redhat.rhevm.vdsm4,bus=virtio-serial0.0,id=port4 -chardev socket,id=channel5,path=/tmp/helloworld5,server,nowait -device virtserialport,nr=5,chardev=channel5,name=com.redhat.rhevm.vdsm5,bus=virtio-serial0.0,id=port5 -chardev socket,id=channel6,path=/tmp/helloworld6,server,nowait -device virtserialport,nr=6,chardev=channel6,name=com.redhat.rhevm.vdsm6,bus=virtio-serial0.0,id=port6 -chardev socket,id=channel7,path=/tmp/helloworld7,server,nowait -device virtserialport,nr=7,chardev=channel7,name=com.redhat.rhevm.vdsm7,bus=virtio-serial0.0,id=port7 -chardev socket,id=channel8,path=/tmp/helloworld8,server,nowait -device virtserialport,nr=8,chardev=channel8,name=com.redhat.rhevm.vdsm8,bus=virtio-serial0.0,id=port8 -chardev socket,id=channel9,path=/tmp/helloworld9,server,nowait -device virtserialport,nr=9,chardev=channel9,name=com.redhat.rhevm.vdsm9,bus=virtio-serial0.0,id=port9 -chardev socket,id=channel10,path=/tmp/helloworld10,server,nowait -device virtserialport,nr=10,chardev=channel10,name=com.redhat.rhevm.vdsm10,bus=virtio-serial0.0,id=port10 -chardev socket,id=channel11,path=/tmp/helloworld11,server,nowait -device virtserialport,nr=11,chardev=channel11,name=com.redhat.rhevm.vdsm11,bus=virtio-serial0.0,id=port11 -chardev socket,id=channel12,path=/tmp/helloworld12,server,nowait -device virtserialport,nr=12,chardev=channel12,name=com.redhat.rhevm.vdsm12,bus=virtio-serial0.0,id=port12 -chardev socket,id=channel13,path=/tmp/helloworld13,server,nowait -device virtserialport,nr=13,chardev=channel13,name=com.redhat.rhevm.vdsm13,bus=virtio-serial0.0,id=port13 -chardev socket,id=channel14,path=/tmp/helloworld14,server,nowait -device virtserialport,nr=14,chardev=channel14,name=com.redhat.rhevm.vdsm14,bus=virtio-serial0.0,id=port14 -chardev socket,id=channel15,path=/tmp/helloworld15,server,nowait -device virtserialport,nr=15,chardev=channel15,name=com.redhat.rhevm.vdsm15,bus=virtio-serial0.0,id=port15 -chardev socket,id=channel16,path=/tmp/helloworld16,server,nowait -device virtserialport,nr=16,chardev=channel16,name=com.redhat.rhevm.vdsm16,bus=virtio-serial0.0,id=port16 -chardev socket,id=channel17,path=/tmp/helloworld17,server,nowait -device virtserialport,nr=17,chardev=channel17,name=com.redhat.rhevm.vdsm17,bus=virtio-serial0.0,id=port17 -chardev socket,id=channel18,path=/tmp/helloworld18,server,nowait -device virtserialport,nr=18,chardev=channel18,name=com.redhat.rhevm.vdsm18,bus=virtio-serial0.0,id=port18 -chardev socket,id=channel19,path=/tmp/helloworld19,server,nowait -device virtserialport,nr=19,chardev=channel19,name=com.redhat.rhevm.vdsm19,bus=virtio-serial0.0,id=port19 -chardev socket,id=channel20,path=/tmp/helloworld20,server,nowait -device virtserialport,nr=20,chardev=channel20,name=com.redhat.rhevm.vdsm20,bus=virtio-serial0.0,id=port20 -chardev socket,id=channel21,path=/tmp/helloworld21,server,nowait -device virtserialport,nr=21,chardev=channel21,name=com.redhat.rhevm.vdsm21,bus=virtio-serial0.0,id=port21 -chardev socket,id=channel22,path=/tmp/helloworld22,server,nowait -device virtserialport,nr=22,chardev=channel22,name=com.redhat.rhevm.vdsm22,bus=virtio-serial0.0,id=port22 -chardev socket,id=channel23,path=/tmp/helloworld23,server,nowait -device virtserialport,nr=23,chardev=channel23,name=com.redhat.rhevm.vdsm23,bus=virtio-serial0.0,id=port23 -chardev socket,id=channel24,path=/tmp/helloworld24,server,nowait -device virtserialport,nr=24,chardev=channel24,name=com.redhat.rhevm.vdsm24,bus=virtio-serial0.0,id=port24 -chardev socket,id=channel25,path=/tmp/helloworld25,server,nowait -device virtserialport,nr=25,chardev=channel25,name=com.redhat.rhevm.vdsm25,bus=virtio-serial0.0,id=port25 -chardev socket,id=channel26,path=/tmp/helloworld26,server,nowait -device virtserialport,nr=26,chardev=channel26,name=com.redhat.rhevm.vdsm26,bus=virtio-serial0.0,id=port26 -chardev socket,id=channel27,path=/tmp/helloworld27,server,nowait -device virtserialport,nr=27,chardev=channel27,name=com.redhat.rhevm.vdsm27,bus=virtio-serial0.0,id=port27 -chardev socket,id=channel28,path=/tmp/helloworld28,server,nowait -device virtserialport,nr=28,chardev=channel28,name=com.redhat.rhevm.vdsm28,bus=virtio-serial0.0,id=port28 -chardev socket,id=channel29,path=/tmp/helloworld29,server,nowait -device virtserialport,nr=29,chardev=channel29,name=com.redhat.rhevm.vdsm29,bus=virtio-serial0.0,id=port29 -chardev socket,id=channel30,path=/tmp/helloworld30,server,nowait -device virtserialport,nr=30,chardev=channel30,name=com.redhat.rhevm.vdsm30,bus=virtio-serial0.0,id=port30 -vnc :1
2.install virtio serial driver in the guest
3.open "Device and Printers"

Actual results:
only 15 ports in the list.

Expected results:
There should be 30 ports.

Additional info: