ovs-brcompatd: Fix sending replies to kernel requests.

ovs-brcompatd: Fix sending replies to kernel requests.

Commit 7d7447 (netlink: Postpone choosing sequence numbers until send
time.) broke ovs-brcompatd because it prevented userspace replies to
kernel requests from using the correct sequence numbers.  This commit fixes
it.

Atzm Watanabe found the root cause and provided an alternative patch to
avoid the problem.

Reported-by: André Ruß <andre.russ@hybris.com>
Reported-by: Atzm Watanabe <atzm@stratosphere.co.jp>
Tested-by: Atzm Watanabe <atzm@stratosphere.co.jp>
Signed-off-by: Ben Pfaff <blp@nicira.com>