net: remove Sock default constructor, it's not necessary

src/test/util/net.h

@@ -106,10 +106,10 @@ constexpr auto ALL_NETWORKS = std::array{
 class StaticContentsSock : public Sock
 {
 public:
-    explicit StaticContentsSock(const std::string& contents) : m_contents{contents}
+    explicit StaticContentsSock(const std::string& contents)
+        : Sock{INVALID_SOCKET},
+          m_contents{contents}
     {
-        // Just a dummy number that is not INVALID_SOCKET.
-        m_socket = INVALID_SOCKET - 1;
     }
 
     ~StaticContentsSock() override { m_socket = INVALID_SOCKET; }
@@ -192,6 +192,11 @@ public:
         return true;
     }
 
+    bool IsConnected(std::string&) const override
+    {
+        return true;
+    }
+
 private:
     const std::string m_contents;
     mutable size_t m_consumed{0};