core: fix issue with search on OSs

* fix the search validation of template
* on UI load - set the search dependencies once the cache population is done - prevents null list of OSs
* make the auto-completion case insensitive
* show the full list when the input is blank

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1003804
Change-Id: I9434189173939ba595862a40483d8da5107228b2
Signed-off-by: Roy Golan <rgolan@redhat.com>