Enforce Treble-only neverallows

This changes SELinuxNeverallowRulesTest so that it enforces
Treble-only neverallows only for Treble devices. The companion
change in system/sepolicy is the one which makes CTS include
Treble-only neverallows and annotate them appropriate so that this
test knows which neverallows are Treble-only.

Test: make cts && \
      cts-tradefed run singleCommand cts --skip-device-info \
          --skip-preconditions --skip-connectivity-check \
          --abi arm64-v8a --module CtsSecurityHostTestCases \
          -t android.cts.security.SELinuxNeverallowRulesTest
Bug: 37082262

Change-Id: I60738d644c0b6bf9ff684a52b62a20b22719bcbb
3 files changed