Add new ls-control command to rescan volatile dir

:Release Notes:
Split roles/services directories into steady and volatile.
Add a new command for ls-control to rescan volatile directories.

:Detailed Notes:

:Testing Performed:
A new test was added. All tests were passed successfully.
Checked on the real system.

:QA Notes:

:Issues Addressed:
[GF-40294] Add new api to LS2 to support scanning specific dir

Open-webOS-DCO-1.0-Signed-off-by: Alekseyev Oleksandr<alekseyev.oleksandr@lge.com>

Change-Id: Ic64d7b4df99df37e91b2131d5bdeea372ea0df6e
Reviewed-on: https://g2g.palm.com/3875
Reviewed-by: DCO Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>