Flush output of ls-monitor promptly

:Release Notes:
Make ls-monitor more real time by flushing its output after every
packet printed.

:Detailed Notes:

:Testing Performed:
Build and manual testing.

:QA Notes:

:Issues Addressed:
[ANG-1449] ls-monitor should flush its output

Open-webOS-DCO-1.0-Signed-off-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>

Change-Id: I3ba6f22f3d09376c9ecf83c6f15a60876a6d8f2d
Reviewed-on: https://g2g.palm.com/4681
Reviewed-by: DCO Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>