mds: wrongly treat symlink inode as normal file/dir when symlink inod…

…e is stale on kcephfs

Signed-off-by: Zhi Zhang <zhangz.david@outlook.com>
(cherry picked from commit 88b6d66)

Conflicts:
	src/mds/Server.cc (hammer has req->head.args.open.flags instead of just flags)

src/mds/Server.cc

@@ -2747,7 +2747,7 @@ void Server::handle_client_open(MDRequestRef& mdr)
     respond_to_request(mdr, -ENXIO);                 // FIXME what error do we want?
     return;
     }*/
-  if ((req->head.args.open.flags & O_DIRECTORY) && !cur->inode.is_dir()) {
+  if ((req->head.args.open.flags & O_DIRECTORY) && !cur->inode.is_dir() && !cur->inode.is_symlink()) {
     dout(7) << "specified O_DIRECTORY on non-directory " << *cur << dendl;
     respond_to_request(mdr, -EINVAL);
     return;