Fix accepting longer PKI keystone auth requests to Barbican

Passing CLI option '-b' during barbican start is not honored by uwsgi.
So, set buffer-size=65535 in /etc/barbican/vassals/barbican-api.ini
Removed redundant '--logto' CLI option to uwsgi.

Change-Id: Icea0144f2c19e916d65c9836ddc9d7e48ecd9412