reorder buildbot steps for speed

[davidsarah]

zooko wrote on 1190#comment:43:

As David-Sarah pointed out in 1190#comment:42, we [were] seeing this VersionConflict on some buildslaves now because I moved the invocation of test-with-fake-dists.py (by the buildmaster) to happen before any build step. (This is necessary because the build step provides a good version of pycryptopp so once it has run then the test-with-fake-dists.py step can't determine how well our setup scripts handle the lack of a good version of pycryptopp...)

On the ticket1306 branch ([4935/ticket1306]), test-with-fake-dists was changed to use a "fakedependency" package, so that it no longer matters what versions of pycryptopp are installed or which version has been built. Once we push this to trunk, test-with-fake-dists can be moved to after 'test', which should still be a good test for that part of #1190, but will be much faster because it won't have to rebuild any of the genuine dependencies. It would also mean that failure to clean up properly after test-with-fake-dists can't affect the main build or test.