Cleanup/expand the filter/query tests
Cleanup/expand the filter/query tests

This patch cleans up duplicate code in Test.Ganeti.Query.Filter and
then adds a test for names consistency with Python's code behaviour
(stable ordering for simple filters and otherwise niceSort'ed
ordering).

Signed-off-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>
Reviewed-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>

ganeti-github-testing/ganeti-test-1,dimara/ganeti,mbakke/ganeti,ganeti/ganeti,bitemyapp/ganeti,dimara/ganeti,ganeti-github-testing/ganeti-test-1,mbakke/ganeti,apyrgio/ganeti,apyrgio/snf-ganeti,leshchevds/ganeti,ganeti/ganeti,mbakke/ganeti,apyrgio/snf-ganeti,yiannist/ganeti,andir/ganeti,leshchevds/ganeti,grnet/snf-ganeti,yiannist/ganeti,grnet/snf-ganeti,andir/ganeti,leshchevds/ganeti,onponomarev/ganeti,ganeti/ganeti,andir/ganeti,yiannist/ganeti,bitemyapp/ganeti,onponomarev/ganeti,apyrgio/ganeti