rbssh wasn't triggering the load of extensions, preventing third-party
SSH storage backends from working. This appears to have regressed at
some point, though I'm unsure how.

We now explicitly initialize Review Board, in order to load extensions.

Moved aside my .ssh directory and cleared away the locally-stored key for

Review Board. Generated a new key with Power Pack and added it to the server's

authorized_keys file. I was able to then log in with the new key through rbssh.
Added some temporary logging statements to verify that the Power Pack SSH storage

backend was being used, and the proper key found.