minor fix to iperf script

cmake_targets/autotests/tools/iperf_script

@@ -39,7 +39,7 @@ timeout=${args[0]}
 iface=${args[1]}
 iperf_args=(${args[@]:2})
 
-ip_client=echo "$iperf_args" | sed -ne 's/.*\-c[ ]*\([0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\).*/\1/p'
+ip_client=`echo "$iperf_args" | sed -ne 's/.*\-c[ ]*\([0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\).*/\1/p'`
 
 #array=${1:-1}
 echo "args =  ${args[@]}"