[keycloak-dev] Conditional testing of cross-dc on Travis

Hi as part of the cross-dc, we need to introduce some means of running cross-dc tests on PRs that touch critical classes. On the other hand, these tests are not necessary for every and each PR as they take 15-20 minutes to complete and for many changes bring no additional value to regular testsuite run. I've implemented a straightforward test for checking whether the given group in travis should be tested [1] and would love to hear your feedback on it. It is intentionally simple, based on filename pattern matching, in the future the checks can become more complex, based on our needs. There are two types of check: - global which is run regardless of the current test group (as defined by .travis.yml). Currently it checks whether only a change in .md documents and if yes, it blocks running the TS - per test-group condition on whether a particular test group should be executed or not (it is "crossdc" group in the PR). If the check is not defined for a given test group, the test group is run (e.g. "server-group1") Thanks --Hynek [1] https://github.com/keycloak/keycloak/pull/4584