autobuild: Remove the os.getpid() from the autobuild directory

autobuild: Remove the os.getpid() from the autobuild directory

This might help our CI runners get a ccache hit by keeping the path constant.

Otherwise, we only get a good ccache hit rate if the docker container gives
us the same pid each time.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>