added new gpg keys to cassandra and rabbitmq repos

Change-Id: Iac7c618d709852599add4c14374031fad3c97f6b
diff --git a/aptly/server/mirror/debian/cassandra.yml b/aptly/server/mirror/debian/cassandra.yml
index 3a19e84..4682dc4 100644
--- a/aptly/server/mirror/debian/cassandra.yml
+++ b/aptly/server/mirror/debian/cassandra.yml
@@ -5,6 +5,7 @@
     mirror_cassandra-21x_distribution: 21x
     mirror_cassandra-21x_components: main
     mirror_cassandra-21x_gpgkeys:
+      - A278B781FE4B2BDA
       - F758CE318D77295D
       - 2B5C1B00
       - 0353B12C