Skip APEX when doing dexopt

APEX is not dex-optimized and doesn't have a valid UID.

Bug: 225756739
Fix: 234312670
Test: tradefed.sh run host --class \
      com.google.android.tradefed.dexoptota.PostRebootTest
Test: tradefed.sh run host --class \
      com.google.android.tradefed.dexoptota.PreRebootTest
Change-Id: I87482f87453ef6bb73c96d4e3a9c8d3cb1d7c428