Currently, when an APEX is staged, apexd moves the file from
/data/app/vmdl*.tmp directory to /data/apex. However, the original file
is labeled with apk_tmp_file and is not readable from apexd.

We plan to resolve this issue by moving the file content via file
descriptor in between the package manager and apexd.

However, until the plan is implemented, temporarily allow apexd to
relabel the file to apex_data_file that is readable to it. This unblocks
the end-to-end test for APEX.

Bug: 112669193
Test: adb install --apex system/apex/apexd/apexd_testdata/test.apex
adb reboot; adb root; adb shell; cmd apexservice getActivePackages
The test APEX is activated

Change-Id: Ib9d4f5c699261f1fa1e6d557731767ee4d7168f9