This patch extends the listener API to include the new parameter
'allowed_cidrs'. This parameter is a list of IPv4 or IPv6 CIDRs. Leaving
this list unset defaults to the traditional behavior of allowing all
ingress traffic to the listener. Setting it will deny all traffic but
all CIDRs set in the 'allowed_cidrs' list.
Note that the API will validate that all CIDRs match the same IP version
of the VIP. This may change later as part of work to allow multiple VIPs
per LB (Change-Id Id7153dbf33b9616d7af685fcf13ad9a79793c06b).
Task: 26210
Story: 2003686
Change-Id: Id2b560df1cde9ce9403afbd593bbaa6cae5f06d6
f3b48bc2f7