Use sh(1), fix bashism

Index: data/gsmartcontrol-root.in
--- data/gsmartcontrol-root.in.orig
+++ data/gsmartcontrol-root.in
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/bin/sh
 ############################################################################
 # Copyright:
 #      (C) 2008 - 2014  Alexander Shaduri <ashaduri 'at' gmail.com>
@@ -93,7 +93,7 @@ fi
 
 if [ "$GSMARTCONTROL_SU" = "" ]; then
 	for subin in $candidates; do
-		which $subin &>/dev/null
+		which $subin >/dev/null 2>&1
 		if [ $? -eq 0 ]; then
 			found_su="$subin";
 			break;
