dirmngr: Suppress error message on trial reading as PEM format.
* dirmngr/dirmngr-client.c (read_pem_certificate): Add NO_ERRMSG argument to suppress the error message. (read_certificate, squid_loop_body): Follow the change.
- GnuPG-bug-id: T5531
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>