syslogd: Do not open console descriptor

Setup consfile filed for logging while Initialized is false, but do not
bother opening the console. Close console/tty descriptors after parsing,
as well. The ttymsg() function will re-open these descriptors for us.

Also, remove references to the ctty global variable since it will always
be _PATH_CONSOLE.

Reviewed by: markj
MFC after: 3 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D41380