Report EditorInfo#packageName based on the actual uid.

This is a follow up CL for Ib871141e3381e45c2623c5f4d692da7a7e78fcc5,
which introduced a verification mechanism between the applicaiton uid
and EditorInfo#packageName reported from the application by using
AppOpsManager#checkPackage.

Regression Bug 21408239 caused by above change is really similar to
the situation we saw in Bug 10688644.  As well explained in the CL
description of Ic04f77b3938585b02fccabbc12d2f0dc62b9ef25, the
system has a special ability to run in the processes of other uids.
Hence we need to use Context#getOpPackageName() instead of
Context#getPackageName() in case components declared by the system
is loaded into another process.

Bug: 18931038
Bug: 21408239
Change-Id: I78510a2ea6ac06cfd5813a23c42f09f70c468493