tmf: Add possibilty to cancel search event requests

tmf: Add possibilty to cancel search event requests

By passing an optional monitor (that will probably come from an
Eclipse job anyway), we can allow the potentially long requests
to be cancelled.

Change-Id: Id8e7d8abf670edd333fc393cfd8d3c1465662a1c
Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Reviewed-on: https://git.eclipse.org/r/76227
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>