add ec2 land support to [no-qa] and [incr] tag

[Ursula Junque]

As part of the orphaned branches story, we need to add support of the [no-qa] tag in the ec2 land script. It should allow branches to be processed only if they have linked bugs or if they have the --no-qa option set, which should add the [no-qa] tag to the commit message. It also should recognize the --incr option, that will require bugs to be linked, and add the [incr] tag to the commit message.

[Launchpad QA Bot (lpqabot)]

Fixed in stable r11268 <http://bazaar.launchpad.net/~launchpad-pqm/launchpad/stable/revision/11268>.