LocationManagerService: Add debug flag lookup from properties

Instead of hardcoding true/false in the code:
 setprop log.LocationManagerService DEBUG
works just fine. Or the reboot-proof version in userdebug/eng builds:
cat > /data/local.prop <<eof
log.tag.LocationManagerService=DEBUG
eof

Change-Id: If4efad1c3adc401c0cb5d1a3cc449b53224ead08