net: do not use atexit for cleanup

This will be necessary in the next patch, which stops using atexit for
character devices; without it, vhost-user and the redirector filter
will cause a use-after-free.  Relying on the ordering of atexit calls
is also brittle, even now that both the network and chardev
subsystems are using atexit.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

vl.c

@@ -4345,9 +4345,6 @@ int main(int argc, char **argv, char **envp)
         qemu_opts_del(icount_opts);
     }
 
-    /* clean up network at qemu process termination */
-    atexit(&net_cleanup);
-
     if (default_net) {
         QemuOptsList *net = qemu_find_opts("net");
         qemu_opts_set(net, NULL, "type", "nic", &error_abort);
@@ -4611,5 +4608,7 @@ int main(int argc, char **argv, char **envp)
     tpm_cleanup();
 #endif
 
+    net_cleanup();
+
     return 0;
 }