BZ #1159390 - Allow open_files_limit & max_connections to be set for galera.

https://bugzilla.redhat.com/show_bug.cgi?id=1159390

They were already being set, but were not params a user could alter.  This patch
makes it so they are.
Merge pull request #438 from jguiditta/BZ1159390-enable-more-galera-overrides

BZ #1159390 - Allow open_files_limit & max_connections to be set for gal...