memfd: don't open kdbus for memfd

No reason to open /dev/kdbus/control if we want memfds. memfd_create() is
always available.

src/shared/memfd.c

@@ -39,16 +39,11 @@ struct sd_memfd {
 
 int sd_memfd_new(sd_memfd **m, const char *name) {
 
-        _cleanup_close_ int kdbus = -1;
         _cleanup_free_ char *g = NULL;
         sd_memfd *n;
 
         assert_return(m, -EINVAL);
 
-        kdbus = open("/dev/kdbus/control", O_RDWR|O_NOCTTY|O_CLOEXEC);
-        if (kdbus < 0)
-                return -errno;
-
         if (name) {
                 /* The kernel side is pretty picky about the character
                  * set here, let's do the usual bus escaping to deal