core: search vms os match and ignore case

search on os matched startsWith instead of equalsIgnoreCase

* Added unit test coverage

Change-Id: I739cad296389ef0356e204ed00b2546bd4d13c92
Signed-off-by: Roy Golan <rgolan@redhat.com>
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1003804