[AppOps] Fix lost op state when upgrading to L.

Root Cause:
The code flow to read appops.xml is called from
ActivityManagerService. In this stage,
PackageManagerService has not initialized yet,
So it is always unable to get application info
to set privileged information.
The original code will always return if uid tag
doesn't have "p" attribute, then it will result
"Unknown element under <pkg>: op" and not able to
read back all data.

Solution:
If source appops.xml has no "p" attribute, add the package
to a list and continue to parse. Then when system is ready,
package manager is available, update privileged information
by the list.

Change-Id: I15bcd46c759d4b8e39bc8fd388c63ecc3f716936