firmware: correctly catch 500, closes #1047

src/opnsense/mvc/app/views/OPNsense/Core/firmware.volt

@@ -92,8 +92,6 @@ POSSIBILITY OF SUCH DAMAGE.
         ajaxCall('/api/core/firmware/upgrade',{upgrade:$.upgrade_action},function() {
             $('#updatelist').empty();
             setTimeout(trackStatus, 500);
-        }).fail(function () {
-            setTimeout(trackStatus, 500);
         });
     }
 
@@ -108,8 +106,6 @@ POSSIBILITY OF SUCH DAMAGE.
         ajaxCall('/api/core/firmware/'+pkg_act+'/'+pkg_name,{},function() {
             $('#updatelist').empty();
             setTimeout(trackStatus, 500);
-        }).fail(function () {
-            setTimeout(trackStatus, 500);
         });
     }
 
@@ -185,6 +181,9 @@ POSSIBILITY OF SUCH DAMAGE.
                 // schedule next poll
                 setTimeout(trackStatus, 500);
             }
+        }).fail(function () {
+            // recover from temporary errors
+            setTimeout(trackStatus, 500);
         });
     }