test client make mirror data source channel open and close all the time

test client make mirror data source channel open and close all the time

This changes the test client so that for the mirror protocol socket,
the lifetime of the connection is decided randomly to last on the order
of a second or so, then the connection is closed and a new one opened when
the close is complete.

This is to enhance testing of connection bringup and teardown especially
in mux case.

The overall functionality remains the same, spamming circles to all clients.

Signed-off-by: Andy Green <andy@warmcat.com>