Chapter 3: check log files - fix tail command

In **chapter 3** at the section **Check log files** the command for printing how many Ansible commands have been executed on each server uses tail instead of cat.

I think the [line](https://github.com/geerlingguy/ansible-for-devops-manuscript/blob/4f14b52476e60c31c331e0a681db394281e4cde7/chapter3.txt#L640) should be
`ansible multi -b -m shell -a "cat /var/log/messages | \
grep ansible-command | wc -l"`
instead of
`ansible multi -b -m shell -a "tail /var/log/messages | \
grep ansible-command | wc -l"`
as description says
> This command shows how many ansible commands have been run on each server
(the numbers you get may be different).

and the `tail` command as I now only print the last 5 lines by default.

The line could also be different according to issue #550

Thank you for awesome book Jeff!

Open chapter3.txt around line 640 and compare the command with the surrounding explanation and issue #550. Update the log-counting example so it matches the stated behavior, then verify the rendered Chapter 3 text shows the corrected command.

Written by the indexing model from the issue text.