Adding net-prerequisites.xml scenario - included in fast & smoke scenarios.

Adding net-setup.xml dependency on arping (sudo apt-get install iputils-arping)

Change-Id: I3276247dc8ae2a2c4ed47801385eb8e50be8f244
diff --git a/tools/test/scenarios/fast.xml b/tools/test/scenarios/fast.xml
index 0d38c45..9d979a8 100644
--- a/tools/test/scenarios/fast.xml
+++ b/tools/test/scenarios/fast.xml
@@ -15,9 +15,10 @@
   -->
 <scenario name="fast" description="ONOS fast smoke test">
     <import file="${ONOS_SCENARIOS}/prerequisites.xml"/>
+    <import file="${ONOS_SCENARIOS}/net-prerequisites.xml"/>
 
     <import file="${ONOS_SCENARIOS}/setup.xml"/>
-    <dependency name="Setup" requires="Prerequisites"/>
+    <dependency name="Setup" requires="Prerequisites,Net-Prerequisites"/>
 
     <import file="${ONOS_SCENARIOS}/net-fast.xml"/>
     <dependency name="Net-Fast" requires="Setup"/>