Fix the wrong reference by CONF

CONF.set_defaults(CONF, web='/usr/share/novnc') should be
CONF.set_default('web', '/usr/share/novnc')

Fixes: bug #1190628
Change-Id: I7ff12d10ed423fa6518b8674b80d0e1cc1787a8b
Merge "Fix the wrong reference by CONF"