buildbot.service: better handle error

fix for 2960

In case of 404, the buildbot.service was storing the 404 error instead of retrying next time

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>

www/base/src/app/common/services/buildbot/buildbot.service.coffee

@@ -106,6 +106,10 @@ class BuildbotService extends Factory
                             elem.on("*", onUpdate).then (unsub) ->
                                 events.push(unsub)
                         return res
+                    , (res) ->
+                        elem.value = null
+                        bound = false
+                        return $q.reject(res)
                 elem.value = p
                 return p
 
@@ -181,4 +185,4 @@ class BuildbotService extends Factory
                 l.push(r.bind($scope))
             return $q.all(l)
         addSomeAndMemoize(self)
-        return self
+        return self