check50 waits and reports wrong remote with a different remote set in config

[Jelleas]

In its remote (not local) operation check50 uses lib50.push to push to GitHub: https://github.com/cs50/check50/blob/5a90acdd2fec699fde7dcef676ecd0e1e290ed07/check50/main.py#L350-L353

Then starts to ping submit.cs50.io (hardcoded) for results. https://github.com/cs50/check50/blob/5a90acdd2fec699fde7dcef676ecd0e1e290ed07/check50/main.py#L184-L192

However, a tool may have set a different remote in its config. In which case check50 will hang for some time, until finally wrongly redirecting to submit.cs50.io.

We discussed this last Summer, but didn't get to implement it it seems. If I remember correctly we settled on redirecting the student immediately to the remote if it was set to something different than submit.cs50.io (rather than ping and wait for results).