VOL-1616 / VOL-1611 : Fix device state issue and memory discrepencies

- Applied mutex on node object to resolve in-memory data conflicts
- Introduced a refresh period for in-memory data

Amendments:

- Fixed node.go file format
- Bumped VERSION to 2.1.0-dev
- Use a RLock for GetLastUpdate

Change-Id: I57e88fe3ec5cceed0d4fcdb240ae9191b49ebe33
diff --git a/db/model/proxy.go b/db/model/proxy.go
index 2933464..d4a86f4 100644
--- a/db/model/proxy.go
+++ b/db/model/proxy.go
@@ -150,6 +150,19 @@
 	PROXY_CREATE
 )
 
+var proxyOperationTypes = []string{
+	"PROXY_GET",
+	"PROXY_LIST",
+	"PROXY_ADD",
+	"PROXY_UPDATE",
+	"PROXY_REMOVE",
+	"PROXY_CREATE",
+}
+
+func (t ProxyOperation) String() string {
+	return proxyOperationTypes[t]
+}
+
 // parseForControlledPath verifies if a proxy path matches a pattern
 // for locations that need to be access controlled.
 func (p *Proxy) parseForControlledPath(path string) (pathLock string, controlled bool) {