ONOS logging on Kafka disabled by default

Logging on Kafka is disabled by default, otherwise a wrong configuration of the
kafka broker can prevent ONOS to log on CLI and files.

Change-Id: I11bb750daa020b636e25c8671f80d26e1e5ab76e
diff --git a/onos/values.yaml b/onos/values.yaml
index 58a5d87..cd01f19 100644
--- a/onos/values.yaml
+++ b/onos/values.yaml
@@ -29,7 +29,7 @@
   registry: ''
 
 kafka_logging:
-  enabled: True
+  enabled: False
   brokers: ['cord-kafka:9092']
 
 nameOverride: ''