MdeModulePkg/UiApp: Connect all devices in UiApp if needed

If the connect all action has not been performed before.
We do it in UiApp now.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdeModulePkg/Application/UiApp/FrontPage.c

@@ -19,7 +19,6 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 
 EFI_GUID   mFrontPageGuid      = FRONT_PAGE_FORMSET_GUID;
 
-BOOLEAN   gConnectAllHappened = FALSE;
 BOOLEAN   mFeaturerSwitch = TRUE;
 BOOLEAN   mResetRequired  = FALSE;
 
@@ -990,9 +989,10 @@ UiEntry (
 
   //
   // Indicate if the connect all has been performed before.
+  // If has not been performed before, do here.
   //
-  if (ConnectAllHappened) {
-    gConnectAllHappened = TRUE;
+  if (!ConnectAllHappened) {
+    EfiBootManagerConnectAll ();
   }
 
   //