fix: address already in use error in dfx start

[mraszyk]

This PR fixes errors of the form

$ dfx start --clean
Running dfx start for version 0.24.2+rev23.dirty-3b68fe37
Using project-specific network 'local' defined in /home/martin/orbit/dfx.json
Error: Failed to get frontend address.
Caused by: Failed to find available socket address
Caused by: Failed to bind socket to 127.0.0.1:4943.
Caused by: Address already in use (os error 98)

observed when restarting dfx shortly after browsing a frontend canister making periodic background requests and stopping dfx.

It has been manually confirmed to fix the issue on Ubuntu 24.04.1 LTS.