zerocloud, all modules: one import per line

Instead of using commas and backslashes for line continuation, having
just one import per line improves readability.

It's also easier to edit imports this way; you can just add or remove
lines. When changes like this are made, the diffs are more readable as
well.
vagrant: don't install zerovm-cli or zpm

These packages install oslo.config 1.2.1. The latest devstack needs
oslo.config 1.4, and these two are incompatible.

Technically, we don't really need the clients in the vagrant box
(although if someone wants to run zvsh, etc., inside the VM in addition
to devstack, this will be a problem). To work around this, we just
install python-swiftclient==2.2.0, which installs oslo.config 1.4.x.
Merge pull request #160 from larsbutler/vagrant-oslo.config-conflict-fix

vagrant: don't install zerovm-cli or zpm
Merge pull request #156 from larsbutler/one-import-per-line

zerocloud, all modules: one import per line