Remove the last pester DB update from the test reminder email function.

This code was in the wrong spot, and was copied to the new location in a
previous commit, however it was not removed from here. Since this function's
purpose is to test the reminder email, there is no reason to update the
last unavailability pester timestamp in the DB.
Process queued items immediately when testing without cron or adding more items

When the 'diagnostic to send test reminder emails' runs it adds items to the
queue, but does not start the workers for the queued items. This starts the
workers without having to run cron and without any additional items being
added to the queue.
Update unavailable reminder/pester criteria to check 'Become Available' date

New criteria for pestering: (1) If unavailable and become available is set,
and if they become available in more than 7 months from now, and they've been
unavailable for more than 6 months, and they have not been pestered in 2
months, then pester. (2) If unavailable and become available is NULL,
if they've been unavailable for more than 6 months, and they have not been
pestered in 2 months, then pester. Many users meet this criteria, so limit
results to 250 users at a time.
Change max run time for processing queued items to 90 seconds.

Locally, it takes a little more than 60 seconds to process all 250 queued
items, so increase the max run time to 90 seconds to ensure all 250 items are
processed so the queue table doesn't fill up.