Add trap to test-unit.sh to shutdown mysql
Add trap to test-unit.sh to shutdown mysql

- When mysql 5.7 unit tests failed, concourse task did not exit
  properly (timed out after 10 hours). We set a trap on the EXIT
  signal to always shutdown the mysql service.

Signed-off-by: Jamil Shamy <1a6c312d8b7ebde5d54d0b4f1a4353b7c149e3bf@pivotal.io>

barthy1/bosh,barthy1/bosh,barthy1/bosh,barthy1/bosh