Integrator hardcodes 'codereview' hostname

Integrator currently operates in gerrit mode if the provided repository happens to contain the string 'codereview'.

The code looks something like this:

if self.source.repo.find('codereview') > -1:
    ...

This is fragile. Also, I have heard that the ultimately intended hostname for gerrit is not intended to be the codereview.qt.nokia.com we are currently using. The hostname could potentially be switched with little warning for us, so this should be fixed soon to avoid a nasty surprise.

We should probably just store in the CI settings whether or not the CI is using gerrit, e.g.

def is_gerrit(self):
    return ("true" == self.git.config("--bool integration.gerrit"))