adevice status working

Ties together the new adevice_fingerprint binary with host fingerprint
function to report diffs.

Reporting UX is not in the final form, but currently looks like:
% adevice status
Device Needs: 2
	system/test_dir
	system/test_dir/test_file
Device Diffs: 1
	system/bin/adevice_fingerprint
Device Extra: 0

Test: atest
Test: mkdir -p $ANDROID_PRODUCT_OUT/system/test_dir && touch $ANDROID_PRODUCT_OUT/system/test_dir/test_file && adevice status

Change-Id: I7d46921387245e25732df931942a4f964fbcff9e
4 files changed