We try to detect apache's version.
Some distributions do not allow launching apache commands (even for detection)
if not root, so we gracefully fall back on 2.4 version configuration file
We alse add an --apache-version option to force the version in case
detection would be wrong.
Closes Bug: #1438773
Change-Id: I7d28c319601cf3919068be4ac52dd10f58a82557