[VOL-1862] rwCore waits for Kafka and KV Store

This commit consists of the following:
1) Make the rw_core wait for kafka and KV Store to be up before
proceeding with its processing.  Previously, rw_core would have
bailed out if kafka/KV was not available. The number of retries
(default=-1, i.e retry forever) and retry interval are both
configurable.

2) Remove a non-json printable variable from the debug log in the
model.

Change-Id: I8d1ef90bf5d202a6f8ae59610aa780292b2844ce
diff --git a/rw_core/config/config.go b/rw_core/config/config.go
index 41d96f4..133b1a4 100644
--- a/rw_core/config/config.go
+++ b/rw_core/config/config.go
@@ -52,6 +52,8 @@
 	default_CoreTimeout               = int64(500)
 	default_CoreBindingKey            = "voltha_backend_name"
 	default_CorePairTopic             = "rwcore_1"
+	default_MaxConnectionRetries      = -1 // retries forever
+	default_ConnectionRetryInterval   = 2  // in seconds
 )
 
 // RWCoreFlags represents the set of configurations used by the read-write core service
@@ -84,6 +86,8 @@
 	DefaultCoreTimeout        int64
 	CoreBindingKey            string
 	CorePairTopic             string
+	MaxConnectionRetries      int
+	ConnectionRetryInterval   int
 }
 
 func init() {
@@ -120,6 +124,8 @@
 		DefaultCoreTimeout:        default_CoreTimeout,
 		CoreBindingKey:            default_CoreBindingKey,
 		CorePairTopic:             default_CorePairTopic,
+		MaxConnectionRetries:      default_MaxConnectionRetries,
+		ConnectionRetryInterval:   default_ConnectionRetryInterval,
 	}
 	return &rwCoreFlag
 }
@@ -201,5 +207,11 @@
 	help = fmt.Sprintf("Core pairing group topic")
 	flag.StringVar(&cf.CorePairTopic, "core_pair_topic", default_CorePairTopic, help)
 
+	help = fmt.Sprintf("The number of retries to connect to a dependent component")
+	flag.IntVar(&(cf.MaxConnectionRetries), "max_connection_retries", default_MaxConnectionRetries, help)
+
+	help = fmt.Sprintf("The number of seconds between each connection retry attempt ")
+	flag.IntVar(&(cf.ConnectionRetryInterval), "connection_retry_interval", default_ConnectionRetryInterval, help)
+
 	flag.Parse()
 }