Fix broken locking so that at least the Python 2.2.1 grp test doesn't

Fix broken locking so that at least the Python 2.2.1 grp test doesn't
lock up.  This really needs to be looked at, as I don't think this
needs to be reentrant.  In any case, several routines call the
__getgrent internal routine and it uses static vars for data.  If this
stuff is really supposed to be threadsafe, then __getgrent probably
needs fixing.