Minor simplifications in bpf_existence_test.

1. Use set instead of vector. This simplifies the code a bit.
2. Use proper NDK constants and functions to check the device
   OS version.

Test: test-only change
Test: passes on flame running qt-dev build (no-op)
Test: passes on flame running RQ3A build
Test: passes on raven running SP2A build
Test: passes on barbet running aosp/master
Change-Id: Ie13e1df674e50fcfb70811bc0dccae515cbb6e1c
1 file changed