Fixed bugs found in further testing.

The cron-job was not thoroughly tested before but has been now.

cloudformation_templates/edx-reference-architecture.json

@@ -1721,7 +1721,7 @@
           "ln -sf ec2-api-tools-* ec2-api-tools\n",
 
           "cat <<'EOF' > /opt/edx/bin/nat_monitor.sh\n",
-          "#!/bin/sh\n",
+          "#!/bin/bash\n",
           "# This script will monitor another NAT instance and take over its routes\n",
           "# if communication with the other instance fails\n",
           "\n",
@@ -1809,7 +1809,7 @@
           "          sleep $Wait_for_Instance_Stop\n",
           "        fi\n",
           "        unhealthy_nat_pingresult=`ping -c $Num_Pings -W $Ping_Timeout $PRIMARY_NAT_IP| grep time= | wc -l`\n",
-          "        if [ \"$unhealthy_nat_pingresult\" != \"$Num_Pings\" ]; then\n",
+          "        if [ \"$unhealthy_nat_pingresult\" == \"$Num_Pings\" ]; then\n",
           "          NAT_HEALTHY=1\n",
           "        fi\n",
           "      done\n",
@@ -1832,7 +1832,7 @@
           "done\n",
           "EOF\n",
           "chmod u+x /opt/edx/bin/nat_monitor.sh\n",
-          "echo '@reboot /root/nat_monitor.sh > /var/log/nat_monitor.log' | crontab\n",
+          "echo '@reboot /opt/edx/bin/nat_monitor.sh > /var/log/nat_monitor.log' | crontab\n",
           "/opt/edx/bin/nat_monitor.sh > /var/log/nat_monitor.log &\n"
         ]]}}
       }