Run regression tests against each commit to "master"

[prakashsurya]

Currently we only build and test pull requests. It'd be great (and probably not much work) to also add a tigger to the regression job to also test each new commit to the master branch, and also have the commit statuses appended to each of those commits. Obviously we shouldn't introduce breakage to the master branch, but sometimes processes fail, so this would be a good way to double check ourselves and quickly get feedback in case something did break on master.

[prakashsurya]

Additionally, this would also let us double check the illumos merge commits as we continually sync with the upstream illumos repository.