apex: do not follow jni_libs from android_app

Because APK-in-APEX embeds its jni_libs in it. We don't have to follow
deps of jni_libs.

Bug: 146992436
Test: m com.android.tethering
      deapexer extract com.android.tethering.apex apex
      ls apex # there should be no /lib dir

Change-Id: Ifa1a6430a420ae7376b155cd59b8ece462cced7e