Stop only the named animation if name is passed

Fixes phaserjs#2299

Author: samme

src/animation/AnimationManager.js

@@ -308,20 +308,9 @@ Phaser.AnimationManager.prototype = {
 
         if (resetFrame === undefined) { resetFrame = false; }
 
-        if (typeof name === 'string')
-        {
-            if (this._anims[name])
-            {
-                this.currentAnim = this._anims[name];
-                this.currentAnim.stop(resetFrame);
-            }
-        }
-        else
+        if (this.currentAnim && (typeof name !== 'string' || name === this.currentAnim.name))
         {
-            if (this.currentAnim)
-            {
-                this.currentAnim.stop(resetFrame);
-            }
+            this.currentAnim.stop(resetFrame);
         }
 
     },