opkg: Put lock file in correct location

:Release Notes:
opkg writes a lock file to /usr/lib. According to the Filesystem
Hierarchy Standard, lock files belong under the /var/lock.

:Detailed Notes:

:Testing Performed:
1) MiniBAT
2) This change was tested as part of the full solution for read-only
   rootfs.

:QA Notes:

:Issues Addressed:
[GF-6589] Update scripts and programs for read-only rootfs

Open-webOS-DCO-1.0-Signed-off-by: Iyad Qumei <iyad.qumei@lge.com>
Change-Id: Ie2f60e241c9d58df6e5a3493aafdade39d8d5867
Reviewed-on: https://g2g.palm.com/2866
Reviewed-by: Build Verification
Reviewed-by: Iyad Qumei <iyad.qumei@lge.com>
Tested-by: Iyad Qumei <iyad.qumei@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>