tests: Add "disable-scdaemon" in gpg-agent.conf.

* tests/openpgp/defs.scm: Add "disable-scdaemon".  Remove
  "scdaemon-program".
* tests/gpgme/gpgme-defs.scm, tests/gpgsm/gpgsm-defs.scm: Likewise.
* tests/inittests, tests/pkits/inittests: Add "disable-scdaemon"

Before this change, running "make check" accesses USB device by
scdaemon on host computer. If there is any smartcard/token available,
it may affect test results. Because default key choice depends on
smartcard/token availability now and existing tests have nothing about
testing smartcard/token, disabling scdaemon is good.

• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>