Create json files on non-volatile storage

:Release Notes:
json files for nyx are installed on /var/cache/nyx

:Detailed Notes:
nyx-utils.conf try to create json files every boot time that could be an
overhead on boot sequence. The json files, device_info.json and
os_info.json, are constant unless S/W update are processed, therefore it
creates the files on non-volatile storage, /var/cache/nyx. For updating
the files, nyx-json-update.sh, which is called by
software-update-complete upstart signal after S/W update, creates a flag
file on /var/cache/nyx and it will tell nyx-utils.conf to update the
files.

:Testing Performed:
miniBAT on verification build
works well creating and updating json files both

:QA Notes:
[BHV-9385] is needed to be merged for updating json files installed on
/var/file-cache/nyx/*.

:Issues Addressed:
[BHV-8110] Propile nyx-utils.conf and find better way to reduce cpu
           cycles
[BHV-9385] delete configuration files after s/w update

Change-Id: I0cb03705d8d9290f6367eb8381257c553cd433f6
Open-webOS-DCO-1.0-Signed-off-by: Changhee Han <ch0.han@lge.com>
Reviewed-on: https://g2g.palm.com/5734
Reviewed-by: DCO Verification
Reviewed-by: Ed Chejlava <ed.chejlava@lge.com>
Reviewed-by: Sangwoo Kang <sangwoo82.kang@lge.com>
Reviewed-by: Changhee Han <ch0.han@lge.com>
Tested-by: Changhee Han <ch0.han@lge.com>
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Merge branch 'develop'