We were running collectstatic as part of our test setup for djblets,

but this wasn't actually necessary, and doing so prevents usage of the

pytest-xdist plugin which is super nice for development. This change

removes it.
While in there, I also changed our pytest_report_header hook to print

the version of djblets and not print the version of django, since the

django version is already printed by the pytest-django plugin.

Ran unit tests, both with xdist and normally.