Revert previous three Mono commits
Revert previous three Mono commits

For now we continue to use pbuilder.

- Revert "[Mono] Drop support for trusty"
- Revert "[Mono] Fix script name"
- Revert "[Mono] Use sbuild for packaging"

This reverts commits 692af98a628dee7a7aaaf3800c5a29b56fc27e9f,
75d1d872cfd6ac652ce08bc909b4ed568be489d9, and
51f941e714bc538ccbdada28214b2aeabe734661.

sillsdev/ci-builder-scripts,sillsdev/ci-builder-scripts,sillsdev/ci-builder-scripts