Prefix the two qa/browsertests jobs with 'qa-'

Follow a discussion with Zeljkof. I would like to vary the template
by project name and targeted hostname.

Jobs renamed:

-browsertests-en.wikipedia.beta.wmflabs.org-linux-firefox
+browsertests-qa-en.wikipedia.beta.wmflabs.org-linux-firefox

-browsertests-test2.wikipedia.org-linux-firefox
+browsertests-qa-test2.wikipedia.org-linux-firefox

Renamed them both manually.

Change-Id: Id7aa42db4daea035517aebe26e1bff6e0445e63f