Add SystemPartitionParseTest to postsubmit

This ignores failures in the other parsing comparison tests
in favor of a specific test that runs through the system APKS on
the device and verifies that no exceptions are thrown.

Bug: 155935153

Test: manual add a broken APK and verify failure in
    SystemPartitionParseTest

Change-Id: I4a02b3dcd8ab993f27c6fc52bb4048d8f2eab273