samba_3_0 disabled in build farm

[Andrew Tridgell]

Jeremy and Jerry,

Following up to my own post ....

I've added a timelimit wrapper that uses process groups and alarm to
kill off any wayward children for all build farm tasks. As long as a
build farm test does not itself change process group then this should
be a reliable way to ensure that no build farm operation takes more
than 30 minutes (thats the limit I set).

The samba3 testing on the farm is still disabled while we try and
cleanup the wayward processes. I've added various bits of shell script
hackery for the affects hosts into the build farm scripts, and once we
see they have recovered we can try enabling the samba3 testing again.

Cheers, Tridge