fix improper use of FailNow in testing

[tsachiherman]

Why this should be merged

This PR addresses a minor issue in testing, which causes the error to be printed as

  	Error:      	failed to bootstrap network: %s
  	Messages:   	failed to start local node: failed to load process context for node "NodeID-7JJiSVewCGTryysCg1kNNzaH3jKjC8FvY" before timeout: context deadline exceeded

instead of

  	Error:      network bootstrapping failed
  	Messages:   network bootstrapping error: failed to load process context for node "NodeID-7JJiSVewCGTryysCg1kNNzaH3jKjC8FvY" before timeout: context deadline exceeded

How this works

The source for the issue was the passing of %s as the first argument to the FailNow method.
Since the method doesn't format the first argument, the output would include the %s.

How this was tested

Tested manually.