Fixes regression in BGP route reflector functionality.

[murali-reddy]

Use proper conversion so correct cluster ID is passed to GoBGP library. GoBGP was complaining:

E1114 19:05:19.722793       1 bgp_peers.go:146] Failed to add node 192.168.56.101 as peer due to route-reflector-cluster-id should be specified as IPv4 address or 32-bit unsigned integer
E1114 19:05:19.723448       1 bgp_peers.go:146] Failed to add node 192.168.56.102 as peer due to route-reflector-cluster-id should be specified as IPv4 address or 32-bit unsigned integer

with out this fix as kube-router was passing wrong cluster-id.

Please use cloudnativelabs/kube-router-git:rr-fix if you would like to test.

[murali-reddy]

Merging based on the user confirmation that functionality works.

https://kubernetes.slack.com/archives/C8DCQGTSB/p1540402541000100