util: always replace g_fsync usage with our wrapper

util: always replace g_fsync usage with our wrapper

g_fsync was introduced in 2.63 which is newer than our minimum
glib version. A future commit will introduce compile time
checking of API versions to prevent accidental usage of APIs
from glib newer than our min declared.

To avoid triggering this warning, however, we need to ensure
that we always use our wrapper function via glibcompat.c,
which will disable the API version warnings.

Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>