integration CI test is (still) flaky

For example, here https://gitlab.torproject.org/Diziet/arti/-/jobs/105083 we see

+ '[' -x ./target/x86_64-unknown-linux-gnu/debug/arti ']'
+ cmd=./target/x86_64-unknown-linux-gnu/debug/arti
+ disown
+ set +e
+ pid=4196
+ sleep 1
+ echo target=networks/basic
+ ./target/x86_64-unknown-linux-gnu/debug/arti proxy -c /builds/Diziet/arti/chutney/net/nodes/arti.toml
+ echo pid=4196
+ wait 4196
$ curl http://example.com -vs --socks5-hostname 127.0.0.1:9150 -o /dev/null
*   Trying 127.0.0.1:9150...
* connect to 127.0.0.1 port 9150 failed: Connection refused
* Failed to connect to 127.0.0.1 port 9150: Connection refused
* Closing connection 0
Cleaning up project directory and file based variables 00:08
ERROR: Job failed: exit code 1

It appears that arti took more than 1s to open its socks listening port. Since !333 (merged) arti doesn't actually do anything that ought to take any time, before then. I think the gitlab runner may have been very overloaded.

We can perhaps improve this after #362