rpc_pipe: remove the clntXX dir if creating the pipe fails

In the event that we create the gssd/clntXX dir, but the pipe creation
subsequently fails, then we should remove the clntXX dir before
returning.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>