Make waitForJobs available to non-SWTBot test plugins

Make waitForJobs available to non-SWTBot test plugins

The waitForJobs pattern is used in a few other places that SWTBot but
they do not have timeouts and the ability to print the stack traces
when it times out. By moving the code to the common plugin, all tests
can use it and benefit from it.

Change-Id: I56a19e5da30216d53a40f44dc3302b427985b1ae
Signed-off-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/81304
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>