ovs-pki: Remove "online PKI" features and ovs-pki-cgi.

ovs-pki: Remove "online PKI" features and ovs-pki-cgi.

Debian bug #683665, Red Hat bug #845350, and CVE-2012-3449 all claim that
ovs-pki's "incoming" directory is a security vulnerability.  I do not think
that this is the case, but I do not know of any users for this feature, so
on balance I prefer to remove it and the ovs-pki-cgi program associated
with it, just to be sure.

CVE-2012-3449.
Bug-report: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=683665
Bug-report: https://bugzilla.redhat.com/show_bug.cgi?id=84535
Reported-by: Andreas Beckmann <debian@abeckmann.de>
Signed-off-by: Ben Pfaff <blp@nicira.com>