buildserver: unpack gradle versions with provisioning shell script

buildserver: unpack gradle versions with provisioning shell script

This was not using anything special from chef, so do it in a shell script
instead.  This makes the script easier for the python/shell people, and
probably uses less memory, since chef is a memory hog.  This might even
make the provision go faster since it uploads the whole script as a file to
the VM, then runs it there.  I think chef sends each command via SSH.