init.qcom.rc: Add a custom shutdown trigger to kill rmtfs am: 66a926c714 am: d3b26ba98f am: 33d78833de am: 248d78eb52 am: 9646666497

Original change: https://android-review.googlesource.com/c/device/linaro/dragonboard/+/1331554

Change-Id: Icf9cdb6adc25f548e16747b4e13f5bc433708f33