pool_test.go reformatting

- uniformed all messages with actual value first, expected second
- clarified error messages
- made comments more readable
- shortened most very long lines

No functional changes.
I don't think it makes the data more readable just because it's wrapped as it's a raw script that does not have a clear structure I can understand anyway. Has it been wrapped according to specific points in the script? Otherwise I think we should just go with this: https://code.google.com/p/go-wiki/wiki/CodeReviewComments#Line_Length