solutions: fix scripts to use /bin/sh

Author: vmaffione

solutions/flowgraph-down.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 set -x
 

solutions/flowgraph-up.sh

@@ -1,10 +1,10 @@
-#!/bin/bash
+#!/bin/sh
 
 set -x
 
 PIDS=""
 
-sudo pkt-gen -i netmap:pipe{1 -f tx -s 10.0.0.1:7000-10.0.0.1:7010 -d 10.0.0.1:8000-10.0.0.1:8004 &> /dev/null &
+sudo pkt-gen -i netmap:pipe{1 -f tx -s 10.0.0.1:7000-10.0.0.1:7010 -d 10.0.0.1:8000-10.0.0.1:8004 2>&1 > /dev/null &
 PIDS="$PIDS $!"
 sleep 0.5
 sudo ./fe -i netmap:pipe}1 -i netmap:pipe{2 -i netmap:pipe{3 -p 8000 -p 8001 &