Set legacy type for VPN

VPN legacy type was lost when NetworkInfo was replaced by
NetworkAgentConfig.
Set legacy type when creating NetworkAgentConfig to fix it.

Original NetworkInfo log:
NI = [type: [], state: CONNECTED/CONNECTED, reason: (unspecified), extra: , failover: false, available: true, roaming: false], Type = -1
Current NetworkInfo log:
NI = [type: VPN[], state: CONNECTED/CONNECTED, reason: (unspecified), extra: , failover: false, available: true, roaming: false], Type = 17

Bug: 184261389
Test: atest CtsHostsideNetworkTests:HostsideVpnTests#testDefault
Change-Id: I237f7ff4d6899530c4ad057a84d3b8b34513be79
diff --git a/services/core/java/com/android/server/connectivity/Vpn.java b/services/core/java/com/android/server/connectivity/Vpn.java
index fd53a10..bf0dda7 100644
--- a/services/core/java/com/android/server/connectivity/Vpn.java
+++ b/services/core/java/com/android/server/connectivity/Vpn.java
@@ -1248,6 +1248,8 @@
         updateState(DetailedState.CONNECTING, "agentConnect");
 
         final NetworkAgentConfig networkAgentConfig = new NetworkAgentConfig.Builder()
+                .setLegacyType(ConnectivityManager.TYPE_VPN)
+                .setLegacyTypeName("VPN")
                 .setBypassableVpn(mConfig.allowBypass && !mLockdown)
                 .build();