The 'vcpucount' command is a getter command for the vCPUu count. When
one or more of the filtering flags are specified the command returns the
value only for the selected combination. In this case the --live and
--config combination isn't valid. This however didn't cause errors as
the combination of flags was rejected by the libvirt API but then the
fallback code kicked in and requested the count in a way where the clash
of the flags didn't matter.
Mark the flag combination mutually exclusive so that users aren't
confused.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1024245
bf45db6041