Nothing drives the transfers while tick() is blocked, e.g. by a prompt
for credentials, so requests which are still connecting time out with
curl error 28. Since #12662 these are retried, but each retry counts
like any other, so a few prompts can use up all of them, and parallel
requests to a private host which timed out that way abort with
"Invalid credentials" once the first of them got credentials, as
AuthHelper only reuses those for a request which was not retried yet.
tick() now keeps track of how long it was blocked between two ticks,
and a request which spent most of its time in that gap is restarted
without counting towards maxRetries.
Fixes#12402
dualfroz
17d32b7184