A dedicated security group (lb-health-mgr-sec-grp) is created for the
Octavia management port but it was unused as the port was created with
no-security-groups.
This commit enables this security group of the health-manager port.
Change-Id: Ib7ec0d194d9858b115ba9343a7117aa1f4d264ea
(cherry picked from commit a767d65dbc)
(cherry picked from commit d76130d0df)