Update the looper "slow message log"

Now you can set `setprop log.looper.1000.main.slow 0` to print all
handler messages. (previously 1 was the minimum allowed value.)

The above example will enable logging for the "main" thread on
UID 1000 (SYSTEM_UID).

Bug: n/a
Test: manual test with `setprop log.looper.1000.main.slow 0; adb shell stop; adb shell start`
and looking at logcat

Test: another manual test, make sure, without the setprop, no logs are printed.

Change-Id: I6172b211b6f01f2fb73a5c57cd93bdb219dca4f4