cli: fix the process exit status codes

[knz]

Found by @jbowens in #70637.
We'll want to backport this. cc @joshimhoff

Release note (bug fix): The exit status of the cockroach command
did not follow the previously-documented table of exit status codes
when an error occurred during the command start-up. (Only errors
occuring after startup were reported using the correct code.)
This defect has been fixed. This bug had existed ever since reference
exit status codes had been introduced.

[cockroach-teamcity]

This change is 

[knz]

blathers backport 21.2

[knz]

blathers backport 21.1

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error creating merge commit from fd9670f8d847b878922b26c01925a5529aec91c9 to blathers/backport-release-21.1-70673: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 21.1 failed. See errors above.

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[jbowens]

thanks!

Reviewed 5 of 5 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @otan)

[knz]

TFYR!

bors r=jbowens

[craig]

Build succeeded:

• GitHub CI (Cockroach)