speed up FuncUtils.verify_*stats

Made the sleep shorter and moved it after the check for the loop condition.
speed up counters.DurationPerFlow
speed up load.FlowModLoad

This test was responsible for about half the runtime of a full OFTest run.
Reduce the number of iterations to shorten it.
load.FlowModLoad: shuffle flow-mods before sending them to the switch

This should cover more code paths than the previous pattern.
base_tests: remove unused clean_shutdown field
controller: move creation of listening connection to constructor

Doing this synchronously results in better error messages.
base_tests: cleanup controller if setup fails
controller: join controller thread in kill()
pktact: remove exact match flows from wildcard priority tests

The OF 1.0 spec states that "An entry that specifies an exact match (i.e., it
has no wildcards) is always the highest priority." The WildcardPriority tests
were incorrect because they expected exact-match flows to be overridden by
wildcard flows with higher priority.

Rather than rework the tests to treat exact-match flows as having the highest
priority I've chosen to replace the exact-match flows with wildcard flows. The
reason is that later versions of OpenFlow do not specify this behavior. Once
the test-groups functionality has been added to OFTest we can add a 1.0-only
test that checks the exact-match priority.

Reported-by: Ben Pfaff <blp@nicira.com>
load.FlowModLoad: cap the number of flow-mods for switches that report huge flowtables
controller: improve log message when sending OF msg
pktact.DirectPacketControllerQueue: skip test if the switch returns an error for the queue stats request on the controller port
flow_matches.ExactMatchPrio: look for packet on exact match flow output port, not wildcard flow output port
Send port_mod message even if features_reply contains no ports
since basic.PortConfigModErr deliberately uses a bogus port number anyway
Don't croak when listing a module with no description