Fix: "Server Offline" should always win against "Please reload"

Nothing to reload if the server is offline, so show the offline message above
the reload one.

CHANGELOG.md

@@ -110,6 +110,9 @@ as shown [in this short GIF](http://i.imgur.com/wp1j9bs.gif).
    reported "HEAD" instead of "(detached"
  * Fixed some path checks for systems with symlinked paths
    ([#1051](https://github.com/foosel/OctoPrint/pull/1051))
+ * Fixed a bug causing the "Server Offline" overlay to pop _under_ the
+   "Please reload" overlay, which could lead to "Connection refused" browser
+   messages when clicking "Reload now" in the wrong moment.
 
 ([Commits](https://github.com/foosel/OctoPrint/compare/1.2.7...1.2.8))
 

src/octoprint/static/less/octoprint.less

@@ -396,10 +396,17 @@ ul.dropdown-menu li a {
   left: 0;
   width: 100%;
   height: 100%;
-  z-index: 10001;
   display: none;
 }
 
+#offline_overlay {
+  z-index: 10002;
+}
+
+#reloadui_overlay {
+  z-index: 10001;
+}
+
 #offline_overlay_background,
 #reloadui_overlay_background {
   position: fixed;