CLOUDSTACK-7664: [UI] Handle change in API response for listloadbalancer

- replaced all occurrences of "listloadbalancerssresponse" with "listloadbalancersresponse" in ui\scripts\vpc.js, following the change in the listLoadBalancers API response string.

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>