call mg_tcpip_free from mg_mgr_free()

test/fuzz.c

@@ -145,9 +145,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     mg_iobuf_add(&c->recv, 0, data, size);
     c->pfn(c, MG_EV_READ, NULL); // manually invoke protocol event handler
 
-    mg_mgr_free(&mgr);
     free(pkt);
-    mg_tcpip_free(&mif);
   }
 
   return 0;

test/mip_tap_test.c

@@ -471,7 +471,6 @@ int main(void) {
 
   // Clear
   mg_mgr_free(&mgr);
-  mg_tcpip_free(&mif);        // Release after mg_mgr
   ASSERT(mgr.conns == NULL);  // Deconstruction OK
   close(fd);
   return 0;

test/mip_test.c

@@ -80,7 +80,6 @@ static void test_poll(void) {
   mg_http_listen(&mgr, "http://127.0.0.1:12346", ph, &count);
   for (i = 0; i < 10; i++) mg_mgr_poll(&mgr, 0);
   ASSERT(count == 10);
-  mg_tcpip_free(&mif);
   mg_mgr_free(&mgr);
 }
 
@@ -240,7 +239,6 @@ static void test_retransmit(void) {
 
   s_driver_data.len = 0;
   mg_mgr_free(&mgr);
-  mg_tcpip_free(&mif);
 }
 
 static void test_frag_recv_path(void) {
@@ -284,7 +282,6 @@ static void test_frag_recv_path(void) {
 
   s_driver_data.len = 0;
   mg_mgr_free(&mgr);
-  mg_tcpip_free(&mif);
 }
 
 static void test_frag_send_path(void) {
@@ -307,7 +304,6 @@ static void test_frag_send_path(void) {
   ASSERT(s_seg_sent == 3);
   s_driver_data.len = 0;
   mg_mgr_free(&mgr);
-  mg_tcpip_free(&mif);
 }
 
 static void test_fragmentation(void) {