only react to connect once

tighten behavior when reacting to connect events.
this will make reconnect work correctly in 0.11.14
see:
https://github.com/dominictarr/reconnect/issues/25
and:
https://github.com/joyent/node/issues/8499

I could have also fixed it in here, https://github.com/dominictarr/reconnect/blob/master/tls.js
but I felt that this change made the reconnect as a whole more robust, so was the better option.