Support absolute paths for SELinux modules

[cosandr]

Hi,

I like to keep forks of roles to a minimum and often refer to files (like your keepalived_selinux_compile_rules list) by absolute paths, usually based on inventory_dir or similar. This isn't supported currently as it assumes each item in that list is a filename. This PR adds a new var for the basename which is used in most places. It has no effect on the default values and shouldn't be a breaking change for existing users as I expect it currently fails with relative paths like it does with absolute ones.

I've also changed the check used for installing SELinux packages to check against the first element in keepalived_selinux_compile_rules instead of hardcoding keepalived_ping, which might be removed by a user overriding the list and thus missing the requirements for compiling modules.

[evrardjp]

I sadly don't have the time to check this in the next weeks.

As selinux coverage was never big, I can't ensure test this myself. Can you confirm it's been tested okay ?

When I will be available, I'll be happy to review and merge as I don't have anything against the idea.

Or, in other words: Looks good at first sight, but need to spend more time on it.

[cosandr]

No worries, I'm not in a rush.

I've tried it by removing all modules it installed and it worked with the default values as well as my own custom policy which is using an absolute path.

[evrardjp]

That's better indeed.