tox: use separate environments for pep8 and pyflakes
tox: use separate environments for pep8 and pyflakes

This should give us better errors when one but not the other fails.
Also named the environments to match the command executed.

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