Issues/484 open311 errors on comment processing

Turn ->find into a ->search to avoid an error or a deprecation warning, as the assumed inviolate (that there will be exactly 1x DB::Alert for the problem spec) seems not to hold.

Asking @struan / @davewhiteland to view, as it might be that this actually *should* have been a single row, and means there's a deeper problem to fix.

Also, I'm getting rather confused by the fact that passing 'suppress_alerts' seems to create sent alerts -- the wording of the test also has this confusion, e.g. should be be renaming to `$alerts_suppressed->count` rather than `$alerts_sent` ?