sd-login: fix sd_seat_get_active() to return ENODATA

This seems to be an oversight from:
    707b66c

We have to return ENODATA instead of ENOENT if a requested entry is
non-present. Also fix the call-site in udev to check for these errors.

Author: David Herrmann

src/libsystemd/sd-login/sd-login.c

@@ -645,10 +645,10 @@ _public_ int sd_seat_get_active(const char *seat, char **session, uid_t *uid) {
                 return r;
 
         if (session && !s)
-                return -ENOENT;
+                return -ENODATA;
 
         if (uid && !t)
-                return -ENOENT;
+                return -ENODATA;
 
         if (uid && t) {
                 r = parse_uid(t, uid);

src/udev/udev-builtin-uaccess.c

@@ -45,7 +45,7 @@ static int builtin_uaccess(struct udev_device *dev, int argc, char *argv[], bool
                 seat = "seat0";
 
         r = sd_seat_get_active(seat, NULL, &uid);
-        if (r == -ENOENT) {
+        if (r == -ENXIO || r == -ENODATA) {
                 /* No active session on this seat */
                 r = 0;
                 goto finish;