qemu_hostdev: Resolve Coverity issue
qemu_hostdev: Resolve Coverity issue

Recent changes uncovered a possibility that 'last_processed_hostdev_vf'
was set to -1 in 'qemuPrepareHostdevPCIDevices' and would cause problems
in for loop end condition in the 'resetvfnetconfig' label if the
variable was never set to 'i' due to 'qemuDomainHostdevNetConfigReplace'
failure.

fabianfreyer/libvirt,zhlcindy/libvirt-1.1.4-maintain,crobinso/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,elmarco/libvirt,cbosdo/libvirt,agx/libvirt,cbosdo/libvirt,VenkatDatta/libvirt,taget/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,datto/libvirt,jardasgit/libvirt,olafhering/libvirt,taget/libvirt,eskultety/libvirt,elmarco/libvirt,VenkatDatta/libvirt,olafhering/libvirt,zippy2/libvirt,andreabolognani/libvirt,zhlcindy/libvirt-1.1.4-maintain,zippy2/libvirt,datto/libvirt,zhlcindy/libvirt-1.1.4-maintain,jfehlig/libvirt,jardasgit/libvirt,eskultety/libvirt,libvirt/libvirt,rlaager/libvirt,agx/libvirt,elmarco/libvirt,zhlcindy/libvirt-1.1.4-maintain,nertpinx/libvirt,jardasgit/libvirt,jfehlig/libvirt,taget/libvirt,nertpinx/libvirt,rlaager/libvirt,nertpinx/libvirt,crobinso/libvirt,taget/libvirt,nertpinx/libvirt,rlaager/libvirt,zhlcindy/libvirt-1.1.4-maintain,datto/libvirt,andreabolognani/libvirt,olafhering/libvirt,andreabolognani/libvirt,crobinso/libvirt,agx/libvirt,datto/libvirt,nertpinx/libvirt,zippy2/libvirt,eskultety/libvirt,agx/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,libvirt/libvirt,shugaoye/libvirt,fabianfreyer/libvirt,olafhering/libvirt,libvirt/libvirt,shugaoye/libvirt,crobinso/libvirt,jfehlig/libvirt,cbosdo/libvirt,shugaoye/libvirt,jardasgit/libvirt,cbosdo/libvirt,libvirt/libvirt,andreabolognani/libvirt,agx/libvirt,elmarco/libvirt,cbosdo/libvirt,elmarco/libvirt,shugaoye/libvirt,shugaoye/libvirt,taget/libvirt,eskultety/libvirt,andreabolognani/libvirt,rlaager/libvirt,zippy2/libvirt,rlaager/libvirt,eskultety/libvirt,datto/libvirt