Report when server severs connection

If an exception occurs while trying to connect to the server (e.g. if the
server has an exception which severs the connection, an unrelated and
unhandled exception is being thrown. This fixes that.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-332
...and in the same vein, a call to action for users to report this to our bug tracker?  In other words, don't hide the fact that this is a shock to us, and get the data channeled to the right place?