[xwalk-2832] create a case to test to call bluetooth.getDefaultAdapter()...

Impacted tests: new 1, update 0, delete 0
Unit test platform: [IVI] crosswalk-10.38.222, t-e-c 0.107
Unit test result summary: pass 0, fail 1, block 0
Does this mean this .wgt doesn't need to be signed? Please check with @jiajiax how to sign a test suite.