Make sure only one onos-mininet operation is going at a time. This script is not mutlithread safe.

Change-Id: I066e9e6ad6405cb32c037502095a2a470eb7c9d5
diff --git a/tools/test/scenarios/net-rest.xml b/tools/test/scenarios/net-rest.xml
index 52a0e03..95f91d1 100644
--- a/tools/test/scenarios/net-rest.xml
+++ b/tools/test/scenarios/net-rest.xml
@@ -123,7 +123,7 @@
               exec="test ${dev4outFlowPort} -ge 1 -a ${dev4outFlowPort} -le 5"/>
 
         <!-- Check that connectivity was established -->
-        <step name="Net-REST.Ping-XY" requires="Net-REST.Create-Intent-XY,Net-REST.Create-Intent-YX"
+        <step name="Net-REST.Ping-XY" requires="^"
               exec="onos-mininet sendAndExpect h1 ping -c1 h4 --expect \ 0% packet loss"/>
         <step name="Net-REST.Ping-YX" requires="^"
               exec="onos-mininet sendAndExpect h4 ping -c1 h1 --expect \ 0% packet loss"/>