syslogd: Block timezone updating in capability mode

[jfree]

Summary

Do not update local timezone data upon reload when syslogd is compiled
with libcasper support. Timezone files are pre-fetched using the
caph_cache_tzdata() function before entering capability mode. Attempts
to re-fetch these files will result in a capability violation.

[markj]

usr.sbin/syslogd/syslogd.c

2479

Let's put an XXX comment in here at least, since we'd like to fix this somehow. It'll require a new interface to the tzcode module.

[jfree]

Add XXX comment for needed future tzcode capability module