hcoop-git-maint: speed up and avoid blocking forever if apache is slow

Previous `find' incantation was actually scanning all the way down
objects/ and refs/. Invert the regex and actually prune. The script
runs in a few seconds rather than a good minute or two now.

Also add a wget timeout so that an unresponsive apache doesn't block
the cron job forever. The cache page isn't really used any more
anyway.