IPv4: Sockets should say can_read() after reading is shut down

This allows clients to get their EOF after shutting down reading.

Kernel/Net/IPv4Socket.cpp

@@ -505,3 +505,9 @@ void IPv4Socket::close()
 {
     shutdown(SHUT_RDWR);
 }
+
+void IPv4Socket::shut_down_for_reading()
+{
+    Socket::shut_down_for_reading();
+    m_can_read = true;
+}

Kernel/Net/IPv4Socket.h

@@ -100,6 +100,8 @@ protected:
     virtual int protocol_allocate_local_port() { return 0; }
     virtual bool protocol_is_disconnected() const { return false; }
 
+    virtual void shut_down_for_reading() override;
+
     void set_local_address(IPv4Address address) { m_local_address = address; }
     void set_peer_address(IPv4Address address) { m_peer_address = address; }