vagrant: make swift config script more flexibile

This makes the swift easier to customize by adding arbitrary config
params to each config file.
vagrant: set log level to DEBUG on object nodes
objectquery: message when x-zerocloud-id is absent

An "Internal Server Error" is raised when the `X-Zerocloud-Id` header is
missing, but the http response body didn't say anything about that. This
change adds a helpful message to the response body explaining the
problem.