Use mainstream only on production build

:Release Notes:
Use mainstream only on production build

:Detailed Notes:
All configuration file for pmlog will be ignored except
default.conf on production build.
All the log messages will be recorded in /var/log/messages.

:Testing Performed:
Compiled locally and tested on emulator and devices.
Added -DWEBOS_MASS_PRODUCTION in CMakelist.txt and installed new
built ipk to nfs.
All the log messages which are not using default context recorded
in /var/log/messages properly.

:QA Notes:

:Issues Addressed:
[GF-11307] Disable context rules for production

Open-webOS-DCO-1.0-Signed-off-by: Hongjeon Ha <hj.ha@lge.com>

Change-Id: Ia84d2058d4dacbb6d89fb8e710375624bc97a669
Reviewed-on: https://g2g.palm.com/3653
Reviewed-by: Build Verification
Reviewed-by: Hongjeon Ha <hj.ha@lge.com>
Tested-by: Hongjeon Ha <hj.ha@lge.com>
Reviewed-by: Keith Derrick <keith.derrick@lge.com>