SchedSwitchHandler: update the exec name of the former process

SchedSwitchHandler: update the exec name of the former process

Update the SchedSwitchHandler class to update the exec name of
the former process as well as the one of the new one. This
allows to keep a 'sort of' up to date exec name in the absence
of other events updating it.

Change-Id: Ie0a1ebc5b64214150edb0b41b62ccaab4447b041
Signed-off-by: Raphaël Beamonte <raphael.beamonte@gmail.com>
Reviewed-on: https://git.eclipse.org/r/70513
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Hudson CI
Reviewed-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Tested-by: Alexandre Montplaisir <alexmonthy@efficios.com>