recovery: Fix the flickering when turning on text mode.

When there's no command specified when booting into debuggable builds
(such as using `adb reboot recovery`), we turn on the text mode (i.e.
recovery menu) directly. This CL fixes the issue to avoid showing the
background image in a flash while turning on the text mode.

Bug: 63985334
Test: `fastboot boot $OUT/recovery.img` and it shows the recovery menu
      directly without the no command image in a flash.
Change-Id: Id86bbe346ab76c8defc95e2b423e695a86774b09
(cherry picked from commit 7022f33ec8)

recovery.cpp

@@ -1591,15 +1591,14 @@ int main(int argc, char **argv) {
             ui->Print("Rebooting automatically.\n");
         }
     } else if (!just_exit) {
-        status = INSTALL_NONE;  // No command specified
-        ui->SetBackground(RecoveryUI::NO_COMMAND);
-
-        // http://b/17489952
-        // If this is an eng or userdebug build, automatically turn on the
-        // text display if no command is specified.
-        if (is_ro_debuggable()) {
-            ui->ShowText(true);
-        }
+      // If this is an eng or userdebug build, automatically turn on the text display if no command
+      // is specified. Note that this should be called before setting the background to avoid
+      // flickering the background image.
+      if (is_ro_debuggable()) {
+        ui->ShowText(true);
+      }
+      status = INSTALL_NONE;  // No command specified
+      ui->SetBackground(RecoveryUI::NO_COMMAND);
     }
 
     if (status == INSTALL_ERROR || status == INSTALL_CORRUPT) {