votequorum: Add cmap key to reset wait_for_all

It's possible in a two_node cluster (and others but it's more likely
with just two) that a node could be booted up after downtime or failure
and the other node is not available for some reason. In this case it
would not be allowed to proceed because wait_for_all is enforced.

This patch provides a cmap key to clear this flag in the desperate
situation where that becomes necessary. It should only be used with
extreme caution and will be wrapped up in pcs which should also check
that fencing has been run.

Signed-Off-By: Christine Caulfield <ccaulfie@redhat.com>
Reviewed-by:  Jan Friesse <jfriesse@redhat.com>