Description of problem:
In rhel7.2 update-device and change-media can be done once. but now it needs to execute twice.

Version-Release number of selected component (if applicable):
libvirt-1.3.2-1.el7.x86_64
qemu-kvm-rhev-2.5.0-2.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. define and start a guest with cdrom device.
# virsh domblklist r72
Target     Source
------------------------------------------------
hdc        /mnt/at-dt/change-media/a.iso
vda        /tmp/zp/r72.qcow2

2. eject cdrom 

# virsh change-media r72 --eject hdc 
error: Failed to complete action eject on media
error: internal error: unable to execute QEMU command 'eject': Tray of device 'drive-ide0-1-0' is not open

# virsh change-media r72 --eject hdc 
Successfully ejected media.


Actual results:
As step2, change-media eject cdrom failed at first time, succeed at the second time.

Expected results:
As the expected result as before, it should be done once. 

Additional info:
In qemu-kvm-rhev-2.5.0-2, the error message after ejecting cdrom is changed.
It is not "is locked" any more. It's "Tray of device xx is not open".
but libvirt is still checking if cdrom "is locked".
......
  if (ret < 0 && c_strcasestr(virJSONValueToString(reply, false), "is locked"))
       ret = -2;
......