(maint) Re-enable Azure PRs on 6.3.x branch
(maint) Re-enable Azure PRs on 6.3.x branch

 - Undoes 39f6bbbd467d0970140a7cddcdf9d42ebdb64d06 which disabled
   builds on this branch.

   Not sure why we did that at the time, but since we're still shiping
   2019.1.2 off of 6.3 and other PRs have targeted the 6.3 branch,
   let's turn Azure back on for pull requests

 - Also reworks the beginning of the file so that it's consistent
   with master branch, which should make it easier to merge up

 - Adds workspace cleanup in

puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb