msg: Make SimpleMessenger shutdown safer

...in the case where no dispatchers were ever added, previously
we would throw an assertion in wait().

Signed-off-by: John Spray <john.spray@inktank.com>
mds: Include parent dirent in lookup_ino response

It's not the full trace, but it's enough for a client to
follow the breadcrumbs back to the root.

Signed-off-by: John Spray <john.spray@inktank.com>
tools: ceph-client-debug

Signed-off-by: John Spray <john.spray@inktank.com>