Cosmetic: Add a way to query the type of a network.

This is a cosmetic change, i.e., there's no change in functionality.

This is the poor man's RTTI. It turns out that maintaining separate lists (or
maps) of the different types of networks gets burdensome pretty quickly
(especially in an upcoming CL where we add functions like
canUserSelectNetwork()).

Change-Id: If5250c0fc106045f681d0fd71278b793addbe1e3
diff --git a/server/VirtualNetwork.cpp b/server/VirtualNetwork.cpp
index bc94d00..37f9644 100644
--- a/server/VirtualNetwork.cpp
+++ b/server/VirtualNetwork.cpp
@@ -51,6 +51,10 @@
     return 0;
 }
 
+Network::Type VirtualNetwork::getType() const {
+    return VIRTUAL;
+}
+
 int VirtualNetwork::addUsers(const UidRanges& uidRanges) {
     for (const std::string& interface : mInterfaces) {
         if (int ret = RouteController::addUsersToVpn(mNetId, interface.c_str(), uidRanges)) {