nspawn: correct EEXIST check when creating directory to mount /tmp in

https://bugs.freedesktop.org/show_bug.cgi?id=86309
(cherry picked from commit 04a9193940)

Conflicts:
	src/nspawn/nspawn.c

src/nspawn/nspawn.c

@@ -818,7 +818,7 @@ static int mount_tmpfs(const char *dest) {
                         return log_oom();
 
                 r = mkdir_label(where, 0755);
-                if (r < 0 && errno != EEXIST) {
+                if (r < 0 && r != EEXIST) {
                         log_error("creating mount point for tmpfs %s failed: %s", where, strerror(-r));
 
                         return r;