Races in group/passwd code (was Re: etc_changed, passwd & group)

[Christopher Faylor <cgf at redhat dot com>]

After consolidating all of the lock code into a "refresh" method,
I realized that there are some pretty big races in the group/passwd
code.  You can't just protect the reading of the buffers against
multiple access, you have to protect all operations which manipulate
the passwd/group buffers since they could be changed out from under
you otherwise.

So, I will have another revamp coming shortly.

cgf