Fix socket close race condition

The server needs to interrupt the sockets on stop, but it must not close
them while other threads may attempt to read from or write to them.

In particular, the video_socket is read by the stream thread, and the
control_socket is written by the controller and read by receiver.

Therefore, close the socket only on sc_server_destroy(), which is called
after all other threads are joined.

Reported by TSAN on close:

    WARNING: ThreadSanitizer: data race (pid=3287612)
      Write of size 8 at 0x7ba000000080 by thread T1:
        #0 close ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:1690 (libtsan.so.0+0x359d8)
        #1 net_close ../app/src/util/net.c:280 (scrcpy+0x23643)
        #2 run_server ../app/src/server.c:772 (scrcpy+0x20047)
        #3 <null> <null> (libSDL2-2.0.so.0+0x905a0)

      Previous read of size 8 at 0x7ba000000080 by thread T16:
        #0 recv ../../../../src/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:6603 (libtsan.so.0+0x4f4a6)
        #1 net_recv_all ../app/src/util/net.c:228 (scrcpy+0x234a9)
        #2 stream_recv_packet ../app/src/stream.c:33 (scrcpy+0x2045c)
        #3 run_stream ../app/src/stream.c:228 (scrcpy+0x21169)
        #4 <null> <null> (libSDL2-2.0.so.0+0x905a0)

Refs ddb9396743

app/src/server.c

@@ -769,12 +769,10 @@ run_server(void *data) {
     // Interrupt sockets to wake up socket blocking calls on the server
     assert(server->video_socket != SC_SOCKET_NONE);
     net_interrupt(server->video_socket);
-    net_close(server->video_socket);
 
     if (server->control_socket != SC_SOCKET_NONE) {
         // There is no control_socket if --no-control is set
         net_interrupt(server->control_socket);
-        net_close(server->control_socket);
     }
 
     // Give some delay for the server to terminate properly
@@ -830,6 +828,13 @@ sc_server_stop(struct sc_server *server) {
 
 void
 sc_server_destroy(struct sc_server *server) {
+    if (server->video_socket != SC_SOCKET_NONE) {
+        net_close(server->video_socket);
+    }
+    if (server->control_socket != SC_SOCKET_NONE) {
+        net_close(server->control_socket);
+    }
+
     sc_server_params_destroy(&server->params);
     sc_intr_destroy(&server->intr);
     sc_cond_destroy(&server->cond_stopped);