[Persistence] Tweak logic

Tweak approach for revision conflict detection; particularly,
use .reject instead of throw to avoid logging of the failure
unnecessarily. WTD-1033.

platform/persistence/elastic/src/ElasticPersistenceProvider.js

@@ -78,11 +78,11 @@ define(
                     // Load the updated model, then reject the promise
                     return get(key).then(function (model) {
                         error.model = model;
-                        throw error;
+                        return $q.reject(error);
                     });
                 }
                 // Reject the promise
-                throw error;
+                return $q.reject(error);
             }
 
             // Check the response to a create/update/delete request;

platform/persistence/queue/src/PersistenceQueueImpl.js

@@ -34,16 +34,18 @@ define(
                 return Object.keys(queue).length === lastObservedSize;
             }
 
+            // Clear the active promise for a queue flush
+            function clearFlushPromise(value) {
+                flushPromise = undefined;
+                activeDefer.resolve(value);
+                return value;
+            }
+
             // Persist all queued objects
             function flush() {
                 // Persist all queued objects
-                flushPromise = handler.persist(queue, objects);
-
-                // When persisted, clear the active promise
-                flushPromise.then(function (value) {
-                    flushPromise = undefined;
-                    activeDefer.resolve(value);
-                });
+                flushPromise = handler.persist(queue, objects)
+                    .then(clearFlushPromise, clearFlushPromise);
 
                 // Reset queue, etc.
                 queue = {};