qemu: Move vm->persistent check into qemuDomainRemoveInactive
So far we have the following pattern occurring over and over
again:
if (!vm->persistent)
qemuDomainRemoveInactive(driver, vm);
It's safe to put the check into the function and save some LoC.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>