Add 'awaiting reviews' with 'CLA not signed'

[matrixise]

Hi,

You can check with this PR, the-knights-who-say-hi add the label CLA not signed but after, bedevere add awaiting review.

Normally, the bedevere should only add awaiting review if the CLA is signed. Is it right?

python/cpython#9840

[brettcannon]

The bots run independent of each other so there is no checking of each other's labels.