Stop encrypted disk on instance suspend/power off

Disconnecting dm-crypt device from an encrypted LVM volume while the instance
is suspended or powered off will secure user data from unauthorized access.
This will extend data at-rest protection provided by the LVM ephemeral storage
encryption feature.

Change-Id: I6070754d998abc73c8a2e03025700da71dcdafbe
Merge "Stop encrypted disk on instance suspend/power off"