Remove incorrect and undocumented connect_nodes(self.nodes[0], 1).
Issue is that transactions are re-relayed (going full circle) between the two nodes, that have two connections between each other.
https://travis-ci.org/github/bitcoin/bitcoin/jobs/679201559#L6992
Also fix some pep8 while touching the file
This bug has been introduced by accident in c1dde3a949b36ce9c2155777b3fa1372e7ed97d8