tests: Make ofproto-dpif tests more resilient.

We have previously used a combination of time/warp and revalidator/wait
to try to synchronize the datapath flow statistics and status up to the
ofproto layer, so that tests may confirm their expected behaviours using
OpenFlow or other protocols operating at that layer of vswitchd (eg LACP).

This patch switches these tests over to using revalidator/purge, which
tells the ofproto-dpif to flush the datapath, causing these statistics
to be updated. In local testing this appears to improve the success rate
of these tests considerably.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
tests: Fix race in async config test.

Occasionally, the testsuite would send the OFPT_SET_ASYNC before
ovs-vswitchd got a chance to send its OFPT_ROLE_REPLY message, causing a
reordering of the testsuite output and a false positive. Give the test
script something extra to do so this is less likely to happen.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
cccl: Respect silent flags.

Automake sets $V to tell the compiler whether to print verbose messages
as it compiles or not. Add support for this variable in cccl, allowing
more quiet build output on windows if the build is configured with
--silent or the developer runs make V=0.

Signed-off-by: Joe Stringer <joestringer@nicira.com>