zpm: abstract `_get_zerocloud_client`
zpm: abstract `_get_zerocloud_client`

This utility can be used elsewhere to handle the various auth args and
create a ZeroCloud client object.

zerovm/zpm,zerovm/zerovm-cli,zerovm/zerovm-cli,zerovm/zerovm-cli,zerovm/zpm,zerovm/zpm,zerovm/zpm,zerovm/zerovm-cli,zerovm/zpm,zerovm/zerovm-cli,zerovm/zpm,zerovm/zerovm-cli