Print warning log for uses of -f/-F on non-ADB UID.

When an app executes the requestsync command with their own UID,
-f and -F cannot be used.

Let's log it on logcat to make it prominent. People often throw away
command output.

Change-Id: Ie0219e9bdea20edc290785f84a101bb546380136
Fixes: 78901672
Test: manual test