BUILD: ssl_ckch: Fix build error about a possible uninitialized value

A build error is reported about the path variable in the switch statement on
the commit type, in cli_io_handler_commit_cafile_crlfile() function. The
enum contains only 2 values, but a default clause has been added to return an
error to make GCC happy.

This patch must be backported as far as 2.5.

src/ssl_ckch.c

@@ -2709,6 +2709,8 @@ static int cli_io_handler_commit_cafile_crlfile(struct appctx *appctx)
 		case CAFILE_CRL:
 			path = crlfile_transaction.path;
 			break;
+		default:
+			goto error;
 	}
 
 	while (1) {