netdev-dummy: add appctl netdev-dummy/conn-state command

Using without any parameter, this command list the connection
state of all netdev-dummy devices that are configured to make
active connections.

Optionally, the name of the netdev-dummy device can be supplied
as a parameter.

The states will be displayed as:

"connected": The socket has been connected to the listener.
"disconnected": The socket is not connected.
"unknown":  It is not an active dummy device.

CC: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>
test: add WAIT_FOR_DUMMY_PORTS helper macro for writing tests

Add a macro to waiting until all ports supplied are connected.

CC: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>
test: Remove explicit sleeps from ofproto-dpif bond tests

Ofproto-dpif bond tests relies on netdev-dummy ports to set up
socket connection before actual tests. The time required
for socket connection varies depends on system load, making the test
prone to failure with simple sleep calls. On the other hand,
conservative sleep value for the slowest machine may be excessive on
a faster machine.

This patch removes the sleep calls. Replace them with
WAIT_FOR_DUMMY_PORTS() introduced in the last patch, thus removing
the timing dependency.

CC: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>