Fix xdump updates not to dump bogus extra updates

Fix xdump updates not to dump bogus extra updates

"xdump updates" believes there are always 15 (UPDATE_TIME_LEN - 1)
scheduled updates.  When fewer than 15 updates are scheduled, it shows
whatever crap update time happens to be in the unused part of
update_time[]: the initial zero or a previously scheduled update.

Root cause is that table EF_UPDATES has always UPDATE_TIME_LEN - 1
entries, which is incorrect when fewer updates are scheduled.  Only
xdump is affected, as the other users ignore the length and stop at
the sentinel.

Fix update_get_schedule() to resize table EF_UPDATES.