Description of problem:
When use 9223372036854775808( the_maximum_of_long_long + 1) for blockjob bandwidth, libvirt reports "argument key 'speed' must not be negative".

Version-Release number of selected component:
libvirt-1.3.3-2.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
virsh # start rhel7.2-1030
Domain rhel7.2-1030 started

virsh # snapshot-create rhel7.2-1030 --disk-only
Domain snapshot 1461044800 created

virsh # blockpull rhel7.2-1030 /var/lib/libvirt/images/rhel6.6-GUI.1461044800 --bytes 9223372036854775808
error: internal error: argument key 'speed' must not be negative

virsh # blockpull rhel7.2-1030 /var/lib/libvirt/images/rhel6.6-GUI.1461044800 --bytes 9223372036854775807
Block Pull started


Actual results:
When use 9223372036854775808( the maximum of long long + 1) for blockjob bandwidth, libvirt reports "argument key 'speed' must not be negative".

Expected results:
Libvirt reports error like this:
error: numerical overflow: 'speed' must be less than 9223372036854775807


Additional info:
Same issue exists with blockcommit/blockcopy/blockjob