In many cases, including devstack and TripleO, the swift account to use
is based on the project_id of the 'service' project, so it makes sense
to use it as a default.
Similarly, the temporary URL key can be fetches from Swift, using HEAD
on the account used to access it.
In both cases it is assumed that the same project is used by Ironic
and Glance to access Swift. Explicit values have to be provided
otherwise.
Finally, the endpoint URL can be fetched from the service catalog. Care
is taken to strip the /v1/AUTH_<tenant ID> suffix.
Closes-Bug: #1737714
Change-Id: I701899928f0f780939f17aabc59eb90593ba95f0