build: Don't assume systemd implies journald
Don't add --with-syslog=journald to extra_distcheck_flags if configured
with systemd (--with-initscript=systemd). Add it if configured with
journald (--with-syslog=journald) instead. This fixes distcheck target
when configured with systemd, but without journald.
Don't install journal.conf helping with enabling journald logging,
unless configured with journald (--with-syslog=journald), as it would be
useless and misleading.
Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>