lib/tst_virt: fix detection when systemd-detect-virt returns 1

When systemd-detect-virt detects no virtualization environment,
it returns 1 as exit code. This leads to tst_is_virt not doing any
fallback tests.

The problem can be reproduced inside a IBM System Z LPAR virtualization
environment.

Signed-off-by: Alexander Egorenkov <[email protected]>
Reviewed-by: Cyril Hrubis <[email protected]>

Author: eaibmz

lib/tst_virt.c

@@ -109,9 +109,9 @@ int tst_is_virt(int virt_type)
 {
 	int ret = try_systemd_detect_virt();
 
-	if (ret >= 0) {
+	if (ret > 0) {
 		if (virt_type == VIRT_ANY)
-			return ret != 0;
+			return 1;
 		else
 			return ret == virt_type;
 	}