More fixes for Fedora and RHEL

Here are a few more fixes for RHEL 7 and Fedora 21.

* The 'security' module is provided by the package 'mod_security' even though everywhere it's referred to as security2.
* I'm not quite sure what to do about PHP. If running under a prefork MPM, the appropriate .so to load is libphp5.so; otherwise it's libphp5-zts.so. For now I've hardcoded it to the latter since this cookbook defaults to the event MPM but this could use some more thought.