api: ContainerCreate: lowercase ErrEmptyConfig

Signed-off-by: Albin Kerouanton <albinker@gmail.com>

runconfig/errors.go

@@ -32,7 +32,7 @@ const (
 	// ErrConflictUTSHostname conflict between the hostname and the UTS mode
 	ErrConflictUTSHostname validationError = "conflicting options: hostname and the UTS mode"
 	// ErrEmptyConfig when container config is nil
-	ErrEmptyConfig validationError = "Config cannot be empty in order to create a container"
+	ErrEmptyConfig validationError = "config cannot be empty in order to create a container"
 )
 
 type validationError string