core: fix search validation of OSs

the UI is validating the input for OSs and was mistakenly
lower casing each input.

this created a corner case where and os unique name with that had
capital letters, windows_2008_R2 was not a valid input for search.

its a false assumption to make that all osinfo unique os name are case
sensitive ATM and no point in trying to refactor that.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1003804
Change-Id: I818dd4eead46402d1fb6a832786020a5458c533d
Signed-off-by: Roy Golan <rgolan@redhat.com>