core: Improve audit_log seach query

This patch improves the performance of the SearchQuery mechanism
for the audit_log table.

Change-Id: I396a90d63a10fc049a37e4792d3e558ff2a7fea3
Bug-Url: https://bugzilla.redhat.com/1056064
Signed-off-by: lzelkha@redhat.com <lzelkha@redhat.com>