virSecurityManagerMetadataLock: Store locked paths
So far, in the lock state we are storing only the file
descriptors of the files we've locked. Therefore, when unlocking
them and something does wrong the only thing we can report is FD
number, which is not user friendly at all. But if we store paths
among with FDs we can do better error reporting.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> Reviewed-by: Peter Krempa <pkrempa@redhat.com>