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/Network.h b/server/Network.h
index e5c929d..6ef0c3a 100644
--- a/server/Network.h
+++ b/server/Network.h
@@ -25,6 +25,11 @@
 // A Network represents a collection of interfaces participating as a single administrative unit.
 class Network {
 public:
+    enum Type {
+        PHYSICAL,
+        VIRTUAL,
+    };
+
     explicit Network(unsigned netId);
 
     // You MUST ensure that no interfaces are still assigned to this network, say by calling
@@ -32,6 +37,8 @@
     // automatically removed interfaces in the destructor, you wouldn't know if it failed.
     virtual ~Network();
 
+    virtual Type getType() const = 0;
+
     bool hasInterface(const std::string& interface) const;
 
     // These return 0 on success or negative errno on failure.