Fix failure to check HIDL return status

Test: run Play Movies and repeat killing
  android.hardware.drm@1.0-service.widevine, check
  log for transaction failed messages.  This uncovered
  a related problem in closeSession which is also fixed
  in this CL.

bug: 64022042
Change-Id: I4e86414aa1625c35689339389391e9fa6d377b1c
Merged-In: I4e86414aa1625c35689339389391e9fa6d377b1c