VOL-1509 : Partial fix for merging issue

- Changed channel map in etcd to a sync.Map
- Changed graph boundaryPorts to sync.Map
- Added logic to check if proxy access is currently reserved
- Changed watch logic to exit when proxy access in progress
- Fixed UpdateAllChildren method
- Commented out the Drop operation again in node.go

Change-Id: I8a61798e907be0ff6b0785dcc70721708308611d
diff --git a/db/model/node.go b/db/model/node.go
index 707fe75..aeac883 100644
--- a/db/model/node.go
+++ b/db/model/node.go
@@ -560,7 +560,7 @@
 
 		// FIXME VOL-1293: the following statement corrupts the kv when using a subproxy (commenting for now)
 		// FIXME VOL-1293 cont'd: need to figure out the required conditions otherwise we are not cleaning up entries
-		branch.GetLatest().Drop(branch.Txid, false)
+		//branch.GetLatest().Drop(branch.Txid, false)
 
 		n.makeLatest(branch, rev, changes)