Remove getHasDns() and VirtualNetwork.mHasDns

getHasDns() and VirtualNetwork.mHasDns are no more useful after commit
aops/658122.

Bug: 116539103
Test: system/netd/tests/runtests.sh pass

Change-Id: Ica04984a954a9e89a5eb38a9b262775d686f8ed4
diff --git a/server/VirtualNetwork.h b/server/VirtualNetwork.h
index e48060b..69b14d8 100644
--- a/server/VirtualNetwork.h
+++ b/server/VirtualNetwork.h
@@ -34,10 +34,9 @@
 // permitted to skip it and pick any other network for their connections.
 class VirtualNetwork : public Network {
 public:
-    VirtualNetwork(unsigned netId, bool hasDns, bool secure);
+    VirtualNetwork(unsigned netId, bool secure);
     virtual ~VirtualNetwork();
 
-    bool getHasDns() const;
     bool isSecure() const;
     bool appliesToUser(uid_t uid) const;
 
@@ -53,7 +52,6 @@
     int maybeCloseSockets(bool add, const UidRanges& uidRanges,
                           const std::set<uid_t>& protectableUsers);
 
-    const bool mHasDns;
     const bool mSecure;
     UidRanges mUidRanges;
 };