ceph: check if LOOKUPNAME request was aborted when filling trace

d_lookup()/d_alloc() require parent inode locked. Parent inode is
not locked if request is aborted.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>