Always show a test target for cmake projects. This will show even
if there are no tests in the project. But I think it is more annoying
*not* to be able to run tests via the locator when tests are available
than getting an error message when attempting that with a project that
does not have tests.

Task-number: QTCREATORBUG-18323
Change-Id: Iba85aa868cb9bfe6c3f44a7ffff620d081d3082f
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>