refactor ping_check

Encapsulate all the neutron specific things you have to do ping a
neutron guest into a separate script. Refactor the main ping_check so
all logic is contained within it.

Change-Id: Ic79d8e3a2473b978551a5635a11dba07e1020bb2
diff --git a/exercises/euca.sh b/exercises/euca.sh
index df5e233..c2957e2 100755
--- a/exercises/euca.sh
+++ b/exercises/euca.sh
@@ -142,7 +142,7 @@
         die $LINENO "Failure authorizing rule in $SECGROUP"
 
     # Test we can ping our floating ip within ASSOCIATE_TIMEOUT seconds
-    ping_check "$PUBLIC_NETWORK_NAME" $FLOATING_IP $ASSOCIATE_TIMEOUT
+    ping_check $FLOATING_IP $ASSOCIATE_TIMEOUT "$PUBLIC_NETWORK_NAME"
 
     # Revoke pinging
     euca-revoke -P icmp -s 0.0.0.0/0 -t -1:-1 $SECGROUP || \