Code review comment for lp:~jelmer/bzr/plugin-refactor

The attached patch refactors the plugin loading code a bit so we
remember the suffix tuple when finding plugins so we can use it for
loading them later. This saves a few stats, and will make it possible
to load individual plugins in the future (this is what I hope to work
on next).

The next step (and my next patch hopefully) will be supporting something like
"bzr --with-plugin /foo/bar/bla".