fork bomb fixed

[Andrew Tridgell]

I've fixed the fork bomb reported on samba-ntdom. It was a bug in some
code I added recently to do background browse synchronisation.

I'm released a new 2.0alpha (alpha5) as this bug can easily bring
machines down. 

Sorry for the slow response on this. I wasn't on the samba-ntdom list
for some reason and didn't know about the problem till Jeremy told me
about it this morning.