camera case fail for testSceneModes

add equals judgement for cts case: android.hardware.camera2.cts.CaptureRequestTest -m testSceneModes
scene-mode (auto) is not single string in some platform, the source is from getCameraCharacteristics
 which contains multiple characters. so previous code == is not correct.

Test: make
Test: run android.hardware.camera2.cts.CaptureRequestTest -m testSceneModes

Change-Id: Ie5ffeeebd0d0c237c80768a4a8217bc04e52a173