distribute: Make server work with multiple remote disks

This change initializes rpc servers associated with disks that are
local. It makes object layer initialization on demand, namely on the
first request to the object layer.

Also adds lock RPC service vendorized minio/dsync

cmd/web-router.go

@@ -30,7 +30,7 @@ import (
 
 // webAPI container for Web API.
 type webAPIHandlers struct {
-	ObjectAPI ObjectLayer
+	ObjectAPI func() ObjectLayer
 }
 
 // indexHandler - Handler to serve index.html