Login failure loop in v5.1.0 go v3-client

[guzzijason]

I'm submitting a ...

• bug report

Traffic Control components affected ...

• Traffic Control Client
• Traffic Ops

Current behavior:

When building go client applications with the TC v5.1.0 v3-client library, we have observed that a login failure (such as resulting from passing incorrect login credentials) results in a looping condition, where a steady stream of login attempts are made against TO API.

Expected behavior:

When invalid login credentials are used, the login attempt should fail immediately, without a apparent retry loop.

Minimal reproduction of the problem with instructions:

Build a client app using github.com/apache/trafficcontrol v5.1.0+incompatible.
Pass invalid login credentials to that app.

Anything else:

Confirmed that building with github.com/apache/trafficcontrol v5.0.0+incompatible does not reproduce the problem.

[rawlinp]

For whoever fixes this:
request() is calling login() if the 1st attempt returned 401. login() eventually makes its way back to request(), which gets another 401, causing it to call login() again, getting stuck in infinite recursion. Instead of calling login(), we should probably make a "raw" login request instead of calling login() which also adds in all the version-retrying.

[srijeet0406]

I can take this one.