lttng: Improve and speed-up control tests handling

lttng: Improve and speed-up control tests handling

For each test a 3 seconds delay is done waiting that the ControlView
is open and initialized properly. This patch optimizes this.

Change-Id: I5308973613c23c481757fd26c84f87c0a9edf94a
Signed-off-by: Bernd Hufmann <Bernd.Hufmann@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/52971
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>