Enhance the test_multicast_between_vms_on_same_network test

This patch is enhancing the test_multicast_between_vms_on_same_network
test to fit the different scenarios that can be encountered when using
multicast:

1) When IGMP snooping is enabled and the multicast group address *is not*
   in the 224.0.0.X range [0], asserts that the multicast traffic *is not*
   flooded.

2) When IGMP snooping is not enabled, asserts that the multicast traffic
   is flooded and the unregistered VM gets it.

3) When IGMP snooping is enabled and the multicast group addres *is* in
   the 224.0.0.X range [0], asserts that the multicast traffic *is*
   flooded.

In order to make those assertions, a new VM is being launched as part of
the test running tcpdump to verify whether the traffic is reaching it or
not.

A new configuration option called "is_igmp_snooping_enabled" has been
added.

[0] https://tools.ietf.org/html/rfc4541 (See section 2.1.2)

Change-Id: I8af041925119463c7199238988f0133e8d993a8f
Signed-off-by: Lucas Alvares Gomes <lucasagomes@gmail.com>
diff --git a/releasenotes/notes/igmp-snooping-8d6d85608df8880a.yaml b/releasenotes/notes/igmp-snooping-8d6d85608df8880a.yaml
new file mode 100644
index 0000000..032be1f
--- /dev/null
+++ b/releasenotes/notes/igmp-snooping-8d6d85608df8880a.yaml
@@ -0,0 +1,11 @@
+---
+features:
+  - |
+    Enhanced the ``test_multicast_between_vms_on_same_network`` adding
+    IGMP test coverage to it. A new VM running tcpdump is spawned as
+    part of the test to verify whether the traffic is reaching it or not.
+upgrade:
+  - |
+    Add a new configuration option called ``is_igmp_snooping_enabled``
+    to enable/disable IGMP testing as part of the
+    ``test_multicast_between_vms_on_same_network`` test case.