In awaitable_hello_fcv_change.js, we

• Send an awaitable hello request to the server
• Change the FCV. This may cause a reconfig also, leading a possible early response to the hello request.
• Resend the hello request if necessary, if we received an early response due to reconfig instead of from the FCV change.

While this is happening, we expect the number of waiting requests until the FCV change is performed to be 1. However, in the window from reconfig, that number may be 0.

We should use an assert.soon instead to wait for this condition to appear.