xs:  Remove redundant validity checks, clean up function headers
xs:  Remove redundant validity checks, clean up function headers

Arguments for driver entry points are checked in libvirt.c, so no need to
check again. Make function entry points consistent.

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