zdtm: don't fail if a test changed cwd

Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm/lib/test.c

@@ -39,6 +39,8 @@ int test_fork_id(int id)
 	return fork();
 }
 
+static int cwd = -1;
+
 #define INPROGRESS ".inprogress"
 static void test_fini(void)
 {
@@ -48,9 +50,9 @@ static void test_fini(void)
 		return;
 
 	snprintf(path, sizeof(path), "%s%s", outfile, INPROGRESS);
-	rename(path, outfile);
+	renameat(cwd, path, cwd, outfile);
 
-	unlink(pidfile);
+	unlinkat(cwd, pidfile, 0);
 }
 
 static void setup_outfile()
@@ -61,6 +63,12 @@ static void setup_outfile()
 		exit(1);
 	}
 
+	cwd = open(".", O_RDONLY);
+	if (cwd < 0) {
+		fprintf(stderr, "Unable to open\n");
+		exit(1);
+	}
+
 	if (atexit(test_fini)) {
 		fprintf(stderr, "Can't register exit function\n");
 		exit(1);