Fail travis build if db/schema.rb is missing commit of update

MSP-11616

Use `git diff --exit-code` to exit with 1 and fail the build if there is
an update to db/schema.rb after `rake db:migrate` runs on travis.
Move git diff --exit-code so build fails instead of errors

MSP-11616

With `git diff --exit-code` in `before_script` it caused the build to
show as errored in travis and didn't turn the merge button red, so try
moving to the `script` section to see if that will make the merge button
red.
Merge branch 'master' into feature/MSP-11616/db-schema-fail

MSP-11616
Diff triggering comment

MSP-11616

Add comment to db/schema.rb so that it will trigger `git diff
--exit-code` to be 1 on travis-ci.
Don't run `bundle exec rake $RAKE_TASK` if `git diff --exit-code` with 1

MSP-11616

Travis runs all entries in the script section even if earlier entries
exit with 1 and only fails the build as a whole once all entries have
run by &&ing together the exit codes.  Running `bundle exec rake
$RAKE_TASK` if the db/schema.rb is missing updates is unnecessary, so
use `&&` in the script section to stop `bundle exec rake $RAKE_TASK`
from running if `git diff --exit-code` exits with 1.
Enable fast_finish on travis-ci

MSP-11616

If any one build fails the entire build will be marked as failed so the
github status can be written back faster.
Revert "Diff triggering comment"

MSP-11616

This reverts commit d5246036c446ca5603d0c97448aff729be97d58a.
Land #4206, fail Travis on schema.rb mismatch

Ensure that the TravisCI build will fail if db/schema.rb is changed
after `rake db:migrate` is run.

MSP-11616 #land