hastd: update assertion for new setgroups/getgroups behavior

We had fixed some of the assertions here, but I had overlooked one more
that doesn't make any sense.  We could coalesce these two at the end,
but I guess it's good to be sure that getgroups(2) doesn't have some
bug where we'll feed userspace a GID if it makes room for it.

Reported by:	S. Ross Gohlke <ross bisd ro>
Fixes:	9da2fe9 ("kern: fix setgroups(2) and getgroups(2) [...]")

Author: kevans91

sbin/hastd/subr.c

@@ -284,7 +284,7 @@ drop_privs(const struct hast_resource *res)
 	PJDLOG_VERIFY(rgid == pw->pw_gid);
 	PJDLOG_VERIFY(egid == pw->pw_gid);
 	PJDLOG_VERIFY(sgid == pw->pw_gid);
-	PJDLOG_VERIFY(getgroups(0, NULL) == 1);
+	PJDLOG_VERIFY(getgroups(0, NULL) == 0);
 	PJDLOG_VERIFY(getgroups(1, gidset) == 0);
 
 	pjdlog_debug(1,