libceph: drop mutex on error in handle_reply()
The osd client mutex is acquired just before getting a reference to
a request in handle_reply(). However the error paths after that
don't drop the mutex before returning as they should.
Drop the mutex after dropping the request reference. Also add a
bad_mutex label at that point and use it so the failed request
lookup case can be handled with the rest.
Signed-off-by: Alex Elder <email@example.com>