Use url.resolve for storageUrl to prevent problems with slashes.

lib/units/device/support/storage.js

@@ -1,4 +1,5 @@
 var util = require('util')
+var url = require('url')
 
 var syrup = require('stf-syrup')
 var Promise = require('bluebird')
@@ -15,7 +16,7 @@ module.exports = syrup.serial()
       var resolver = Promise.defer()
 
       var req = request.post({
-          url: util.format('%ss/api/v1/%s', options.storageUrl, type)
+          url: url.resolve(options.storageUrl, util.format('s/api/v1/%s', type))
         }
       , function(err, res, body) {
           if (err) {