Use environment-uuid when interacting with MAAS

Use environment-uuid when interacting with MAAS

The environment-uuid is passed - as agent_name - to MAAS when acquiring
and listing nodes. This will allow multiple Juju environments to coexist
in a single MAAS user's account.

In addition, it prevents environment-uuid from being set in
environments.yaml, and returns an appropriate error message. This is
intended to stop people from inadvertently clobbering existing
environments.

It also starts cleaning up MAAS's providerSuite by dropping the environ
attribute in favour of makeEnviron(). The former was initialised to a
half-working environ that caused strange test failures.

https://code.launchpad.net/~allenap/juju-core/maas-environment-uuid-use/+merge/191249

(do not edit description out of merge proposal)

[allenap, 2013-10-15 17:00:27]

Please take a look.

[allenap, 2013-10-15 17:03:10]

Please take a look.

[thumper, 2013-10-15 21:38:03]

LGTM - with one question and one concern.

What does older MAAS installs do with unexpected GET parameters?  When the new
agent_name field is passed through, is this going to cause problems with older
systems?  Also, I wonder where we should document the required versions.

I foresee a problem when a new juju is running against an older MAAS, the new
agent_name is passed through, and also passed through as a filter when listing. 
Is the unknown field similarly ignored by the filter code?

https://codereview.appspot.com/14644045/diff/4001/provider/maas/config.go
File provider/maas/config.go (right):

https://codereview.appspot.com/14644045/diff/4001/provider/maas/config.go#new...
provider/maas/config.go:23: "environment-uuid": schema.String(),
I do think that we should move this into the general environ config, but this
can happen later.  For expediency, I'm happy to have this just in MAAS for now.

https://codereview.appspot.com/14644045/diff/4001/provider/maas/environ.go
File provider/maas/environ.go (right):

https://codereview.appspot.com/14644045/diff/4001/provider/maas/environ.go#ne...
provider/maas/environ.go:174: acquireParams.Add("agent_name",
environ.ecfg().maasEnvironmentUUID())
Is "agent_name" a new MAAS parameter? The current docs don't list it.

https://codereview.appspot.com/14644045/diff/4001/provider/maas/environ.go#ne...
provider/maas/environ.go:326: filter.Add("agent_name",
environ.ecfg().maasEnvironmentUUID())
Beautiful :-)

https://codereview.appspot.com/14644045/diff/4001/provider/maas/environprovid...
File provider/maas/environprovider.go (right):

https://codereview.appspot.com/14644045/diff/4001/provider/maas/environprovid...
provider/maas/environprovider.go:45: attrs := cfg.UnknownAttrs()
Didn't this bit land as r1984 on lp:juju-core?

https://codereview.appspot.com/14644045/diff/4001/provider/maas/instance_test.go
File provider/maas/instance_test.go (right):

https://codereview.appspot.com/14644045/diff/4001/provider/maas/instance_test...
provider/maas/instance_test.go:39: func (s *instanceTest)
TestStringWithoutHostname(c *gc.C) {
Thank you.  There is a tendency in some juju tests to have too much tested in
one test.