crabclient does not check proxy expiration when using --proxy

When running crab client with an expired proxy passed via `--proxy` option, crab client fails with the cryptic message

```plaintext
Singularity> crab status -d crab_recover_20230925_162750 --proxy=$X509_USER_PROXY
Fatal error trying to connect to https://cmsweb-test11.cern.ch:8443/crabserver/devtwo/info?subresource=version using subresource=version.
The server answered with an error.
Log file is /path/to/crab.log
```

maybe we can do better and check if the proxy is valid beforehand.

I will assign low priority because I know that this is usually not a problem, since the user is supposed to be responsible of his own proxy if he uses the `--proxy` option.

fyi: @novicecpp