Can't use dotnet-svcutil behind authenticated proxy

**Describe the bug**
The dotnet-svcutil tool doesn't work behind a corporate proxy that requires authentication. It just keeps asking for the username and password in a loop

**To Reproduce**
Steps to reproduce the behavior:
1. Get behind a authenticated corporate proxy (in this case with Kerberos auth)
2. Run dotnet-svcutil
3. Put username and password in, it'll keep asking
4. If using wireshark, notice that a 407 authenticationrequired response is returned

**Expected behavior**
It manages to authenticate with the proxy and generates client proxy

**Workaround**
Download all files with a web browser, then run the tool on the locally downloaded files