Motivation
In machines with more complex network topologies it is possible for us
to have multiple possible NICs we might want to use for a request. Users
may wish to vary this on a per-request or even a per-client basis.
This control can typically be expressed by offering a local address to
bind to before making the connection attempt.
Modifications
Allow users to express a preferred local address at request or client
scope.
Make this part of the connection pool key.
Bind the local address when specified.
Test all of this.
Results
More capable clients.
