Fix cannot specify custom path for built-in profiles on Windows

[dan-petty]

Fix paths misconfigured if build-in profile with same name exists

[dan-petty]

#161219

[dan-petty]

@microsoft-github-policy-service agree

[dan-petty]

To test set a custom path for "Git Bash" profile in settings.json:

    "terminal.integrated.profiles.windows": {
        "Git Bash": {
            "path": "C:\\custom\\path\\to\\git\\bin\\bash.exe"
        }
    }

[Tyriar]

I have a little trouble reproducing, I think because the git bash source picks up my install, but this fix looks good and safe 👍