[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/db/model/node.go b/db/model/node.go
index fcd3b5f..c9815fa 100644
--- a/db/model/node.go
+++ b/db/model/node.go
@@ -457,7 +457,7 @@
 	n.mutex.Lock()
 	defer n.mutex.Unlock()
 
-	log.Debugw("node-update-request", log.Fields{"path": path, "strict": strict, "txid": txid, "makeBranch": makeBranch})
+	log.Debugw("node-update-request", log.Fields{"path": path, "strict": strict, "txid": txid})
 
 	for strings.HasPrefix(path, "/") {
 		path = path[1:]
@@ -626,7 +626,7 @@
 	n.mutex.Lock()
 	defer n.mutex.Unlock()
 
-	log.Debugw("node-add-request", log.Fields{"path": path, "txid": txid, "makeBranch": makeBranch})
+	log.Debugw("node-add-request", log.Fields{"path": path, "txid": txid})
 
 	for strings.HasPrefix(path, "/") {
 		path = path[1:]