Acquire partial wakelock for inattentive sleep tests

Acquire a partial wakelock during inattentive sleep tests
to prevent the device from suspending when put to sleep.

Bug: 203045501
Test: atest InattentiveSleepTests
Change-Id: I342f8d3dd4f1eb7fbd40b3fbcabf7418b2ed6e45
(cherry picked from commit ba57d7a09db671c99656e0820849ca5c1cc0dc3e)
3 files changed