base-files: Add bbappend to mount /var/db/temp at tmpfs

:Release Notes:
Allocate storage in RAM for com.palm.tempdb by adding a tmpfs entry for
/var/db/temp to /etc/fstab. Its size is set to 32MB.

:Detailed Notes:
Added validation for fstab to ensure that only one record exists per
mount-point.

:Testing Performed:
Verified that build of base-files produced a package with correct
contents (folders with correct permissions and fstab).

:QA Notes:

:Issues Addressed:
[GF-1826]  DB8: Qualify support of in-memory database
[GF-23954] CCC: Add base-files=webos1

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>

Change-Id: I9e6dd5800627e9d8c9c051fd7b54c38620cb7403
Reviewed-on: https://g2g.palm.com/2688
Reviewed-by: Build Verification
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Tested-by: Susan Montooth <susan.montooth@lge.com>