Merge ~ahasenack/qa-regression-testing:apache-2.4.33-wont-start-ssl-compression into qa-regression-testing:master

Cope with apache 2.4.32 and higher no longer starting when ssl compression is requested but not provided by openssl.

I'm updating cosmic's apache from 2.4.29 to 2.4.33 and this triggered a test error in qa-regression-testing/scripts/test-apache2.py:
======================================================================
FAIL: test_cve_2012_4929_on (__main__.BasicTest)
Test CVE-2012-4929 (compression on)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "scripts/test-apache2.py", line 527, in test_cve_2012_4929_on
  File "/home/ubuntu/git/qa-regression-testing/scripts/testlib_httpd.py", line 287, in _prepare_ssl
    self._enable_mod("ssl")
  File "/home/ubuntu/git/qa-regression-testing/scripts/testlib_httpd.py", line 186, in _enable_mod
    self._restart()
  File "/home/ubuntu/git/qa-regression-testing/scripts/testlib_httpd.py", line 283, in _restart
    self._start()
  File "/home/ubuntu/git/qa-regression-testing/scripts/testlib_httpd.py", line 107, in _start
    self.assertEqual(expected, rc, result + report)
AssertionError: Got exit code 1, expected 0
Starting apache2 (via systemctl): apache2.serviceJob for apache2.service failed because the control process exited with error code.
See "systemctl status apache2.service" and "journalctl -xe" for details.
 failed!

What happened there is that since apache 2.4.32 (see http://www.apache.org/dist/httpd/CHANGES_2.4.32, search for SSLCompression) it is considered an error to enable SSL compression if the openssl build doesn't support it.

The test suite adds "SSLCompression on" to the default site, then calls _prepare_ssl() which will eventually restart apache. The restart action is guarded by an "apachectl -t" call, which fails because of the above reason, failing the whole test.

I've seen that there are some exceptions in test_cve_2012_4929_on for similar reasons, because (according to the test) since 14.04 we don't offer ssl with compression, but in those versions at least apache would start. That is no longer the case.

This patch will catch the failure in _prepare_ssl() and check if apachectl -t failed because of this problem. If that's the case, the test is skipped (should it succeed instead?) with a message. If apachectl succeeds, or fails for a different reason, then the original exception from _prepare_ssl() is raised and the test fails.