Speed up tests by removing uneeded permuations

[nirs]

Test simple was 20 times, each run with 1..20 iterations of the
reconnecting code. This consumed about half of the test time for no
value.

Now we run only one time, using 20 iterations.

[ionelmc]

When I did it, it was effectively a poor man's stress test. It even catch some bugs: https://travis-ci.org/ionelmc/python-manhole/jobs/10214295#L237

We should still have something (slow, annoying and inefficient) like this, at least for the stress suite from #14

[nirs]

Well the current test is still slow and annoying, taking about 4 seconds to make 20 re-connections. Do you like to have more then 20 iterations?

For long term, the regular tests should check one reconnect, and the stress tests should be configurable, so you can run it for minutes or hours as needed.

[ionelmc]

Fine, lets continue in #14