Ignore errors about missing smartcard daemon.

It's an OPTION on FreeBSD, but 2.1.21 treated missing scdaemon as an
error.

PR: 219400
Submitted by: Philip Jocks
Obtained from: https://dev.gnupg.org/rGa8dd96826f8484c0ae93c954035b95c2a75c80f2
See also: https://lists.gnupg.org/pipermail/gnupg-users/2017-May/058233.html
MFH: 2017Q2