introduce kafka replication.factor (#20)

Change-Id: Ic4f7178d1815e835db7fb657cb46d70bfdb2940c
diff --git a/opencontrail/files/3.0/server.properties b/opencontrail/files/3.0/server.properties
index 5cdaee6..091346c 100644
--- a/opencontrail/files/3.0/server.properties
+++ b/opencontrail/files/3.0/server.properties
@@ -120,3 +120,6 @@
 # Timeout in ms for connecting to zookeeper
 log.cleanup.policy=compact
 delete.topic.enable=true
+
+default.replication.factor={% if database.members|length>1 %}2{% else %}1{% endif %}
+