Unit tests for odd uses of Bootstrap()

[Ian Denhardt]

As discussed in #320, There are a few scenarios that are not tested well (if at all), related to strange uses of Conn.Bootstrap():

• calling Conn.Bootstrap() more than once on the same connection
• doing things with the connection after a failed bootstrap other than closing it.

We ought to write some tests that check for these scenarios explicitly.

I consider this relatively low priority though, since bugs caught by such tests would be unlikely to affect many real world applications.