Fix pluralization of seconds

[dnicolson]

This is similar to #16586.

Can be tested with:

curl --retry 2 xxx

Before:

curl: (6) Could not resolve host: xxx
Warning: Problem : timeout. Will retry in 1 seconds. 2 retries left.
curl: (6) Could not resolve host: xxx
Warning: Problem : timeout. Will retry in 2 seconds. 1 retry left.
curl: (6) Could not resolve host: xxx

After:

curl: (6) Could not resolve host: xxx
Warning: Problem : timeout. Will retry in 1 second. 2 retries left.
curl: (6) Could not resolve host: xxx
Warning: Problem : timeout. Will retry in 2 seconds. 1 retry left.
curl: (6) Could not resolve host: xxx
``

[bagder]

Thanks!