Simulation not producing blocks/txs when using a single peer

[jansegre]

Should we create an issue to handle it later?

Originally posted by @msbrogli in #393 (comment)

This was discovered on a PR that will be merged soon. Apparently the tests that fall on this behavior aren't hiding any bugs, that is, fixing this behavior doesn't seems like it would uncover a bug. I've worked around this on another test by just adding a dummy peer, which seems to trigger the "transaction adding".

[jansegre]

This still happens for come reason, although it doesn't have impact on any tests. See https://github.com/HathorNetwork/hathor-core/blob/master/tests/simulation/test_simulator.py#L19-L31