scd: Restrict use of DEVINFO --watch command for socket connection.
* scd/app.c (app_send_devinfo): Return GPG_ERR_INV_HANDLE when it's not socket when KEEP_LOOPING != 0.
(cherry picked from commit d98521b934ec6a5abb0ad18e39a26009a8806c52)
- GnuPG-bug-id: T7151
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>