Make the support loader activity display UI.

This lets us show a loader before jumping into the support UI.

Bug: 63117391
Test: Manual
Change-Id: Ie9660f7e89cc02d59e24798f22ca9cd0ef11701d

AndroidManifest.xml

@@ -3074,7 +3074,7 @@
         <activity android:name=".support.SupportDashboardActivity"
                   android:label="@string/page_tab_title_support"
                   android:icon="@drawable/ic_help"
-                  android:theme="@android:style/Theme.NoDisplay"
+                  android:theme="@android:style/Theme.DeviceDefault.Light.Panel"
                   android:enabled="@bool/config_support_enabled">
             <intent-filter android:priority="-2">
                 <action android:name="com.android.settings.action.SETTINGS"/>

src/com/android/settings/support/SupportDashboardActivity.java

@@ -47,8 +47,8 @@ public class SupportDashboardActivity extends Activity implements Indexable {
             supportFeatureProvider.startSupportV2(this);
         } else {
             startActivity(new Intent(this, LegacySupportActivity.class));
+            finish();
         }
-        finish();
     }
 
     /**