Revert "Remove DNS build tests (they'll be fixed later)"

This reverts commit dd00a9b65be2cf44b6b2c6bff0ac91dadb386ea1.
It's something
Add a build test fixture
Add some tests
"Finish" DNS build tests; fix some broken things
Do verbosity in dhcp_build too
Change DNS build test fixture name
Don't try to add files when empty=True
Write a DHCP build test
Fix some verbosity and directory name issues
Remove unused module
Add extra files for testing

(Our build process requires them.)
Get up to date
Merge branch 'master' into build_tests
Remove initial_data data from test fixtures
Add some DNS sanity check tests
Move DNS tests around; fix a couple minor things
Change test system id for no reason
Add some more DHCP tests
Specify remote to fix Git issue