libct/cg.WriteCgroupProcs: improve errors

No need to add a file name to the error messages, as errors from
OpenFile and (*os.File).Write both contain the file name already.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/cgroups/utils.go

@@ -352,7 +352,7 @@ func WriteCgroupProc(dir string, pid int) error {
 
 	file, err := OpenFile(dir, CgroupProcesses, os.O_WRONLY)
 	if err != nil {
-		return fmt.Errorf("failed to write %v to %v: %w", pid, CgroupProcesses, err)
+		return fmt.Errorf("failed to write %v: %w", pid, err)
 	}
 	defer file.Close()
 
@@ -369,7 +369,7 @@ func WriteCgroupProc(dir string, pid int) error {
 			continue
 		}
 
-		return fmt.Errorf("failed to write %v to %v: %w", pid, CgroupProcesses, err)
+		return fmt.Errorf("failed to write %v: %w", pid, err)
 	}
 	return err
 }