tests: Fixes test-io-channel-socket.c tests under msys2/mingw

Currently test-io-channel-socket doesn't init with
qemu_init_main_loop
and that's cause the qemu_aio_context not inited,
and the following is the stack when null pointer accessed:

qemu_fd_register (c:\work\xemu\qemu\util\main-loop.c:336)
qemu_try_set_nonblock (c:\work\xemu\qemu\util\oslib-win32.c:224)
qemu_set_nonblock (c:\work\xemu\qemu\util\oslib-win32.c:230)
socket_can_bind_connect (c:\work\xemu\qemu\tests\socket-helpers.c:93)
socket_check_protocol_support (c:\work\xemu\qemu\tests\socket-helpers.c:141)
main (c:\work\xemu\qemu\tests\test-io-channel-socket.c:568)
__tmainCRTStartup (@__tmainCRTStartup:142)
mainCRTStartup (@1400014f6..140001539:3)
BaseThreadInitThunk (@BaseThreadInitThunk:9)
RtlUserThreadStart (@RtlUserThreadStart:12)

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200915121318.247-18-luoyonggang@gmail.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/test-io-channel-socket.c

@@ -25,6 +25,7 @@
 #include "socket-helpers.h"
 #include "qapi/error.h"
 #include "qemu/module.h"
+#include "qemu/main-loop.h"
 
 
 static void test_io_channel_set_socket_bufs(QIOChannel *src,
@@ -556,6 +557,7 @@ int main(int argc, char **argv)
     bool has_ipv4, has_ipv6;
 
     module_call_init(MODULE_INIT_QOM);
+    qemu_init_main_loop(&error_abort);
     socket_init();
 
     g_test_init(&argc, &argv, NULL);