haproxy: Allow setting the tune.bufsize and tune.chksize options
crowbar-pacemaker: Increase tune.bufsize option of haproxy

The default value (16384) is too small for keystone: getting a PKI token
from its ID fails with a 400 Bad Request message from haproxy because
the URI path is too long.
Merge pull request #142 from vuntz/haproxy-bufsize

Fix issue with keystone/HA not working because of default haproxy setting