Updates to test_develop_pull_request update subjobs

Hi all,

Ori sent a pin to develop today[1] for the fast_gettext gem, however the
update17 subjob was still failing. Since these jobs are (I think) meant to
test db migrations on the currently supported versions, it seemed right to
update them to test against 1.11-stable and 1.12-stable.

So, I've updated the subjobs to be update111 and update112 repsectively.
However, update112 was still failing, as it also required the gem
pinning[2], so I've cherry-picked that commit. Update111 is fine because
the Gemfile in 1.11-stable already defines a lower version of

TL;DR test_develop_pull_request should be working again, but you may need
to kick the tests if you sent PRs in the last day or so.


[2] https://github.com/theforeman/foreman/blob/1.11-stable/Gemfile#L23
ยทยทยท -- Greg IRC: gwmngilfen