Special casing for Ironic VIRT_DRIVER in exercises

Ironic on Devstack does not currently suppport security groups or
anything volume related.  Add some special casing so exercises can
be run without error against the Ironic driver.

Change-Id: I2a54d8cca06fc17894e74b4401af9423cef95635
diff --git a/exercises/floating_ips.sh b/exercises/floating_ips.sh
index 1416d4d..7e90e5a 100755
--- a/exercises/floating_ips.sh
+++ b/exercises/floating_ips.sh
@@ -180,7 +180,7 @@
 fi
 
 # FIXME (anthony): make xs support security groups
-if [ "$VIRT_DRIVER" != "xenserver" -a "$VIRT_DRIVER" != "openvz" ]; then
+if [ "$VIRT_DRIVER" != "ironic" -a "$VIRT_DRIVER" != "xenserver" -a "$VIRT_DRIVER" != "openvz" ]; then
     # Test we can aren't able to ping our floating ip within ASSOCIATE_TIMEOUT seconds
     ping_check "$PUBLIC_NETWORK_NAME" $FLOATING_IP $ASSOCIATE_TIMEOUT Fail
 fi