VPN screen clean up

Fix: 35960168
Fix: 35856128
Test: visual
- Increase new vpn dialog padding
- Update VPN icon

Change-Id: Ibc7f4fc5b9eff24693a25542e7d3481fbe3c393d

res/layout/vpn_dialog.xml

@@ -20,7 +20,7 @@
     <LinearLayout android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:orientation="vertical"
-            android:padding="8dp">
+            android:padding="24dp">
 
         <LinearLayout android:id="@+id/editor"
                 android:layout_width="match_parent"

src/com/android/settings/vpn2/LegacyVpnPreference.java

@@ -34,7 +34,7 @@ public class LegacyVpnPreference extends ManageablePreference {
 
     LegacyVpnPreference(Context context) {
         super(context, null /* attrs */);
-        setIcon(R.mipmap.ic_launcher_settings);
+        setIcon(R.drawable.ic_settings_24dp);
     }
 
     public VpnProfile getProfile() {