Backing out the whenConnected support for now. I convinced myself that the
extra features in Twisted issue 4735 are useful and fairly easy to add on
top of the current implementation but I think this code needs to make it
into the Twisted branch before it makes sense to work on that.

Revert "Add support for whenConnected as suggested in TwistedMatric issue 4735."

This reverts commit 449d333df6390e7024e9a3c0d8b898b3b0521859.