Fix failure to check HIDL return status

HIDL transaction status wasn't being checked
resulting in a SIGABRT from createPlugin when the
remote process dies.

bug: 64441780
test: run Play Movies and repeat killing
  android.hardware.drm@1.0-service.widevine, check
  log for transaction failed messages.

Change-Id: I0ea70578d60bb84cf693f158963181781d7e35c3