On CentOS 7, an SELinux denial occurs when keepalived tries to read
haproxy's PID file. This patch adds SELinux policy to allow this
activity and breaks the SELinux compilation part of the role into
a reusable set of tasks.

Keepalived role doesn't need HAProxy pid SELinux permissions.
Therefore the keepalived_haproxy_pid_file was removed from
the list of rules to compile.

However, flexibility could be advisable, and the list of rules
to compile should not be static, but instead be an overridable
list. By default, the list will compile the ping rule, as it
was done before, for retro-compatibility.

But a deployer can now provide path to files to compile.