Implement mgmt REST APIs to heal storage format. (#3604)

* Implement heal format REST API handler
* Implement admin peer rpc handler to re-initialize storage
* Implement HealFormat API in pkg/madmin
* Update pkg/madmin API.md to incl. HealFormat
* Added unit tests for ReInitDisks rpc handler and HealFormatHandler

cmd/server-main.go

@@ -418,6 +418,12 @@ func serverMain(c *cli.Context) {
 		fatalIf(initDsyncNodes(endpoints), "Unable to initialize distributed locking clients")
 	}
 
+	// Set globalIsXL if erasure code backend is about to be
+	// initialized for the given endpoints.
+	if len(endpoints) > 1 {
+		globalIsXL = true
+	}
+
 	// Initialize name space lock.
 	initNSLock(globalIsDistXL)
 
@@ -453,6 +459,9 @@ func serverMain(c *cli.Context) {
 		fatalIf(apiServer.ListenAndServe(cert, key), "Failed to start minio server.")
 	}()
 
+	// Set endpoints of []*url.URL type to globalEndpoints.
+	globalEndpoints = endpoints
+
 	newObject, err := newObjectLayer(srvConfig)
 	fatalIf(err, "Initializing object layer failed")