Make CopyEscapable consistent with Copy and return nil in case of success instead of io.EOF

Upstream-commit: 77c94175bdc387e7f43876f7097b970f67116054
Component: engine

components/engine/utils/utils.go

@@ -543,7 +543,7 @@ func CopyEscapable(dst io.Writer, src io.ReadCloser) (written int64, err error)
 					if err := src.Close(); err != nil {
 						return 0, err
 					}
-					return 0, io.EOF
+					return 0, nil
 				}
 			}
 			// ---- End of docker