zerovm-cli: add zerovm-cli jenkins scripts

I had to add back in the `get_ip` function in order to be able to scp
the test and coverage reports out of the container and publish them in
the jenkins job.
buildenv.sh: remove use of lxc-attach

`lxc-attach` is not supported on our deployment platform (Ubuntu 12.04).
See https://help.ubuntu.com/lts/serverguide/lxc.html.
zerovm-cli: remove some redundant calls to get_ip