logging: allow inode/offset params to be NULL
logging: allow inode/offset params to be NULL

Not all callers of virLogManagerDomainOpenLogFile will
care about getting the current inode/offset, so we should
allow those parameters to be NULL

Signed-off-by: Daniel P. Berrange <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

jardasgit/libvirt,jfehlig/libvirt,nertpinx/libvirt,olafhering/libvirt,crobinso/libvirt,taget/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,eskultety/libvirt,zippy2/libvirt,eskultety/libvirt,taget/libvirt,taget/libvirt,taget/libvirt,fabianfreyer/libvirt,eskultety/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,nertpinx/libvirt,eskultety/libvirt,datto/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,crobinso/libvirt,fabianfreyer/libvirt,datto/libvirt,taget/libvirt,eskultety/libvirt,jfehlig/libvirt,crobinso/libvirt,zippy2/libvirt,datto/libvirt,andreabolognani/libvirt,jfehlig/libvirt,jardasgit/libvirt,nertpinx/libvirt,olafhering/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,crobinso/libvirt,libvirt/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,olafhering/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,nertpinx/libvirt,zippy2/libvirt,datto/libvirt,jardasgit/libvirt,jfehlig/libvirt,VenkatDatta/libvirt,libvirt/libvirt,olafhering/libvirt,datto/libvirt,libvirt/libvirt,libvirt/libvirt,zippy2/libvirt