zdtm: Make it possible for test to get ZDTM_NEWNS variable

I will need to make cgroup test behave slightly differently
when it's in and out of ns/ run. To do so it's handy to use
the ZDTM_NEWNS variable set by zdtm.sh
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/lib/ns.c

@@ -169,7 +169,7 @@ int ns_exec(void *_arg)
 	if (prepare_mntns())
 		return -1;
 
-	setenv("ZDTM_EXE", "1", 0);
+	setenv("ZDTM_NEWNS", "2", 1);
 	execvp(args->argv[0], args->argv);
 	fprintf(stderr, "exec(%s) failed: %m\n", args->argv[0]);
 	return -1;
@@ -206,6 +206,7 @@ int ns_init(int argc, char **argv)
 		fprintf(stderr, "fork() failed: %m\n");
 		exit(1);
 	} else if (pid == 0) {
+		setenv("ZDTM_NEWNS", "3", 1);
 		ret = execvp(argv[0], argv);
 		fprintf(stderr, "exec(%s) failed: %m\n", argv[0]);
 		return ret;

test/zdtm/lib/test.c

@@ -105,18 +105,19 @@ void test_init(int argc, char **argv)
 
 	val = getenv("ZDTM_NEWNS");
 	if (val) {
-		unsetenv("ZDTM_NEWNS");
-		ns_create(argc, argv);
-		exit(1);
-	}
+		if (!strcmp(val, "1")) {
+			ns_create(argc, argv);
+			exit(1);
+		}
 
-	val = getenv("ZDTM_EXE");
-	if (val) {
-		test_log_init(outfile, "ns");
-		redir_stdfds();
-		unsetenv("ZDTM_EXE");
-		ns_init(argc, argv);
-		exit(1);
+		if (!strcmp(val, "2")) {
+			test_log_init(outfile, "ns");
+			redir_stdfds();
+			ns_init(argc, argv);
+			exit(1);
+		}
+
+		/* "3" -- run the test */
 	}
 
 	val = getenv("ZDTM_GID");