Check I/O scheds before writing

Signed-off-by: Tyler Nijmeh <tylernij@gmail.com>

system/bin/ktweak

@@ -180,8 +180,15 @@ fi
 # I/O
 for queue in /sys/block/*/queue/
 do
-	_write "${queue}scheduler" cfq
-	_write "${queue}scheduler" kyber
+	avail_scheds=`cat "${queue}scheduler"`
+	for sched in cfq noop kyber none
+	do
+		if [[ "$avail_scheds" == *"$sched"* ]]
+		then
+			_write "${queue}scheduler" "$sched"
+			break
+		fi
+	done
 	write "${queue}iostats" 0
 	write "${queue}read_ahead_kb" 64
 	write "${queue}nr_requests" 64