This commit added ovn_sb_connection to octavia.conf otherwise it will
try to connect to ovn-sb-db using the default address which is
127.0.0.1 while the ovn-sb-db listen on the IP address of the
api_interface.
Closes-Bug: #1950111
Change-Id: I9cb9a0365d00ffd70562b4b3e83493ec09bd52c2