Use `arg` and `env` from cliutils: v1_1/shell

To remove aliases for `arg` and `env` functions in novaclient.utils,
we should use `arg` and `env` directly from cliutils in novaclients modules.
This is the first stage: change usage in novaclient.v1_1.shell

Change-Id: I237f0473844de49db8a4b141a9a71603c9ac76a7