fd-util: accept that kcmp might fail with EPERM/EACCES

In a container the kcmp call might well be blocked; Accept that and fall
back to fstat in that case.

src/basic/fd-util.c

@@ -277,7 +277,7 @@ int same_fd(int a, int b) {
                 return true;
         if (r > 0)
                 return false;
-        if (errno != ENOSYS)
+        if (!IN_SET(errno, ENOSYS, EACCES, EPERM))
                 return -errno;
 
         /* We don't have kcmp(), use fstat() instead. */