forecast.HRRR_ESRL model does not work

[wholmgren]

Describe the bug
The HRRR_ESRL model does not work because:

1. The query variables are out of date
2. The Unidata THREDDS server /best data archive is bad or at least inconsistent with other models in a way that I can't figure out.

Versions:

• pvlib.__version__: 0.6.1

Additional context
#698 adds commented out sections to address the variable issue. For the test suite, it's better that it continues to be broken due to the variables than for the requests to the weird data to through. So, leaving it in the more broken state for now.

I'm not going to fix this myself, but pull request welcome.