Update vpn icon from setting gear to vpn key.

Change-Id: Ic135d5e28a0547e949c8170f985e4de26e05ad51
Fix: 37781101
Test: visual
diff --git a/src/com/android/settings/vpn2/LegacyVpnPreference.java b/src/com/android/settings/vpn2/LegacyVpnPreference.java
index a4d7221..4ef2808 100644
--- a/src/com/android/settings/vpn2/LegacyVpnPreference.java
+++ b/src/com/android/settings/vpn2/LegacyVpnPreference.java
@@ -34,7 +34,7 @@
 
     LegacyVpnPreference(Context context) {
         super(context, null /* attrs */);
-        setIcon(R.drawable.ic_settings_24dp);
+        setIcon(R.drawable.ic_vpn_key);
     }
 
     public VpnProfile getProfile() {