Add a shell command to update mIsOffBody

This CL adds a shell command to updade mIsOffBody. This will later be
used in setup_wear.sh for lab testing.

Bug: 272528508
Test: Start a emualtor and issue the command
sijiec@sijiec:~/master_workspace/main$ adb shell dumpsys deviceidle force-offbody
mForceIsOffBody: true
mIsOffBody: true
sijiec@sijiec:~/master_workspace/main$ adb shell dumpsys deviceidle force-onbody
mForceIsOffBody: true
mIsOffBody: false

Change-Id: Ife80a402b1856d9fd36c2069b98d6b2291299f06