zdtm: say no to EINTR

Everyone have known that EINTR is returned due to cpt/rst.
But it's error, we forgot to set SA_RESTART;).

test/zdtm/lib/test.c

@@ -83,6 +83,7 @@ void test_init(int argc, char **argv)
 	static FILE *pidf;
 	struct sigaction sa = {
 		.sa_handler	= sig_hand,
+		.sa_flags	= SA_RESTART,
 	};
 	sigemptyset(&sa.sa_mask);