chore(testing): add ability to skip GAE Flex tests

[ace-n]

Related to b/173545239 and #1242

[bshaffer]

Hmm, so we don't actually want to skip all flex tests. We just want to skip flex DEPLOYMENT tests. I think we could do this by:

1. Adding a check in each GAE flex deployment test to verify RUN_FLEX_DEPLOYMENT_TESTS should be true. This could be done by adding this to every appengine/flexible/*/test/DeployTest.php file:

   /** @beforeClass */
   public static function checkFlexDeploymentEnvVar()
   {
       self::requireEnv('RUN_FLEX_DEPLOYMENT_TESTS');
   }

2. Add a block to run_test_suite.sh to temporarily set RUN_DEPLOYMENT_TESTS to false if the directory contains an app.yaml with env: flex. I can't really see a good/elegant way to do that with the current script though, so I prefer option 1

[ace-n]

Add a block to run_test_suite.sh to temporarily set RUN_DEPLOYMENT_TESTS to false if the directory contains an app.yaml with env: flex. I can't really see a good/elegant way to do that with the current script though, so I prefer option 1

We already do this - that's what the grep in run_test_suite.sh is for. 🙂

[bshaffer]

Looks great! Should we skip the deployment test in endpoints/getting-started as well? I believe so!