Set the ip_address_mode according to scale out configuration. This is done to support ECMP with allowed address pair changes. Reviewed with https://review.opencontrail.org/#/c/904/

Change-Id: Iacd0698b8f0ab02c6caaf36e6176014d83621883
Merge "Set the ip_address_mode according to scale out configuration. This is done to support ECMP with allowed address pair changes. Reviewed with https://review.opencontrail.org/#/c/904/" into R1.10