Fix a couple path-related issues with rb-site and rbssh.
Review Request #3463 — Created Oct. 30, 2012 and submitted
Fix a couple path-related issues with rb-site and rbssh. rb-site wasn't using the data directory as $HOME, and rbssh wasn't being given the current PYTHONPATH. These weren't problems before, but became issues with the new SSHDB key store. We now set $HOME in rb-site to what we expect, and we pass sys.path as PYTHONPATH when executing anything from an SCMTool.
Tested that rb-site was using the correct $HOME when importing keys. Tested that rbssh was no longer failing to work with sshdb (on a production install, it couldn't find settings_local).