Remove MaxConnsPerHost settings to avoid potential hangs (#10438)

MaxConnsPerHost can potentially hang a call without any
way to timeout, we do not need this setting for our proxy
and gateway implementations instead IdleConn settings are
good enough.

Also ensure to use NewRequestWithContext and make sure to
take the disks offline only for network errors.

Fixes #10304

cmd/admin-handlers.go

@@ -1677,11 +1677,6 @@ func checkConnection(endpointStr string, timeout time.Duration) error {
 	ctx, cancel := context.WithTimeout(GlobalContext, timeout)
 	defer cancel()
 
-	req, err := http.NewRequest(http.MethodHead, endpointStr, nil)
-	if err != nil {
-		return err
-	}
-
 	client := &http.Client{Transport: &http.Transport{
 		Proxy:                 http.ProxyFromEnvironment,
 		DialContext:           xhttp.NewCustomDialContext(timeout),
@@ -1696,11 +1691,15 @@ func checkConnection(endpointStr string, timeout time.Duration) error {
 	}}
 	defer client.CloseIdleConnections()
 
-	resp, err := client.Do(req.WithContext(ctx))
+	req, err := http.NewRequestWithContext(ctx, http.MethodHead, endpointStr, nil)
+	if err != nil {
+		return err
+	}
+
+	resp, err := client.Do(req)
 	if err != nil {
 		return err
 	}
 	defer xhttp.DrainBody(resp.Body)
-	resp.Body.Close()
 	return nil
 }