src/daemon/utils_time.c: Pass "struct tm *" to format_zone().

This is a partial revert of e2cb258c7b6ce456f4119fd1454c85b479fa3e2d:
strptime() does not look the local timezone up itself but gets the
information from the "struct tm". If that is initialized with {0}, it
will always return the "+0000" time zone.