search: disable the lucene_search icinga check

No idea what it does but it has been CRITICAL for 158d, so clearly it's
not _that_ CRITICAL. Stop if from spamming us, especially since it's
unlikely anyway will care anytime soon about it.

Change-Id: I8008c459a925ae070365a37ed04d5ca217de96b5
Merge "search: disable the lucene_search icinga check" into production