util: Alter virAuthGet*Path API return processing
util: Alter virAuthGet*Path API return processing

If we never find the valid credtype in the list, then we'd return
NULL without an error signaled forcing the caller to generate one
that will probably be incorrect. Let's be specific.

Signed-off-by: John Ferlan <87558058f6f829e5ec976c8ef960720af4ff9c7d@redhat.com>
Reviewed-by: Marcos Paulo de Souza <0b4ebe3a213a49a2bc3457b98408e6d86812eb46@gmail.com>

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