Fix handling of lb server certificates
Fix handling of lb server certificates

Previously, if a user specified an ARN for the `server_certificate` key
in a listener spec, the LB creation would succeed, but future updates
would always update the server_certificate.  If the user specified an
ARN for the `ssl_certificate_id`, the creation would succeed, but future
updates would fail.  Here we support both.

chef/chef-provisioning-aws,getaroom/chef-provisioning-aws,ii/chef-provisioning-aws,Fodoj/chef-provisioning-aws,dcallao/chef-provisioning-aws,msonnabaum/chef-provisioning-aws,Mindera/chef-provisioning-aws,tarak/chef-provisioning-aws,Jimflip/chef-provisioning-aws,redterror/chef-provisioning-aws,miguelcnf/chef-provisioning-aws,chef/chef-provisioning-aws,RyanJarv/chef-provisioning-aws,dblessing/chef-provisioning-aws,mikenairn/chef-provisioning-aws,dawudrahmanaqovia/chef-provisioning-aws