Use non-wakeable alarm for data-stall alarm.

Previous behavior with use of ELAPSED_REALTIME_WAKEUP would wake up
the device for data stall check if device is in sleep state.

It should be safe to defer data stall check until device wakes up
from sleep.  Update to use ELAPSED_REALTIME instead.

Bug: 36221436
Test: Compile test.
Change-Id: I057214c655910aedf4c87cba45a041e527047ac9