Avoid spinning in the connection monitor thread

Apparently the vconn_*_wait functions actually don't block till
an interesting event occurs, but rather "arrange the poll loop
to wake up". The caller needs to invoke poll_block() to block for
those events. Without this, the connection monitor thread was
simply spinning.
Also, made a few minor changes to the connection-test code.

Change-Id: Icccb1be9bd1731bfb5aaac5e1abc602add3dec80
Signed-off-by: Amit Bose <bose@noironetworks.com>