added cassandra validation and maintenance playbooks

cassandra-maintenance.yml

diff --git a/cassandra-maintenance.yml b/cassandra-maintenance.yml
index a4cca0a..0a48bc7 100644
--- a/cassandra-maintenance.yml
+++ b/cassandra-maintenance.yml
@@ -4,4 +4,4 @@
   serial: 1
   roles:
   - { role: apigee-opdk-cassandra-rebuild, opdk_region: 'dc-1' }
-  - { role: apigee-opdk-cassandra-repair }
+#  - { role: apigee-opdk-cassandra-repair }