fix: proxy requests to honor global transport

* fix: proxy requests to honor global transport 
Load the globalProxyEndpoint properly

also, currently, the proxy requests will fail silently for batch cancel
even if the proxy fails; instead,d properly send the corresponding error back
for such proxy failures if opted

* pass the transport to the GetProxyEnpoints function

---------

Co-authored-by: Praveen raj Mani <praveen@minio.io>

cmd/endpoint.go

@@ -1194,7 +1194,7 @@ func GetProxyEndpointLocalIndex(proxyEps []ProxyEndpoint) int {
 }
 
 // GetProxyEndpoints - get all endpoints that can be used to proxy list request.
-func GetProxyEndpoints(endpointServerPools EndpointServerPools) []ProxyEndpoint {
+func GetProxyEndpoints(endpointServerPools EndpointServerPools, transport http.RoundTripper) []ProxyEndpoint {
 	var proxyEps []ProxyEndpoint
 
 	proxyEpSet := set.NewStringSet()
@@ -1213,7 +1213,7 @@ func GetProxyEndpoints(endpointServerPools EndpointServerPools) []ProxyEndpoint
 
 			proxyEps = append(proxyEps, ProxyEndpoint{
 				Endpoint:  endpoint,
-				Transport: globalRemoteTargetTransport,
+				Transport: transport,
 			})
 		}
 	}