Convert BootStatsHostTest to JUnit4 and use Assume

If the API level is not met, use assumption failure to
notify that the device didn't meet the requirements.

Test: ./cts-tradefed run cts-dev -m CtsBootStatsTestCases -n -a armeabi-v7a
Bug: 140110369
Change-Id: Ib9c4bcd6b557ce8291f3a00290c7cc400b4391ee
1 file changed