Upgrade Groovy: Fix travisci compile problem

[kmanning]

• PR for Issue Provide a hook for arbitrary scripts after 'apply' #250 caused travisCI build to fail with the error message > BUG! exception in phase 'class generation' in source unit '/home/travis/build/manheim/terraform-pipeline/test/HookPointTest.groovy' unsupported Target MODULE
• Example failing build: https://travis-ci.com/github/manheim/terraform-pipeline/builds/209643807
• The problem seems to be related to java - https://issues.apache.org/jira/browse/GROOVY-8235
• JobDSL Plugin v1.77 has upgraded groovy to 2.4.12. Upgrading terraform-pipeline from 2.4.11 to 2.4.12 seems to address the compile failure in travisCI