Change sync-tools to use API

environs/sync now operates on two interfaces:
 - a ToolsFinder, which is used for finding
   tools in the destination
 - a ToolsUploader, which is used for uploading
   missing tools to the destination

There are two implementations of ToolsFinder
and ToolsUploader: one using Storage, and one
that uses the client API.

In cmd/juju we now use the client API unless
--local-dir is specified. --public now only
takes effect if --local-dir is specified. This
is redundant anyway, given the metadata plugins.
Fix race in test.
Rework auth checks for gccgo.
simplify the change
Simplify more
Merge pull request #633 from howbazaar/fix-gccgo-failure

Rework auth checks for gccgo.

gccgo has problems comparing concrete types and interfaces. I'm betting it is actually only interfaces implemented by non-pointer types, but hey, I'm not a compiler writer.\

Reworks the auth checks.
Add doc comments for sync-tools changes
Merge pull request #625 from axw/synctools-api

Change sync-tools to use API

environs/sync now operates on two interfaces:
 - a ToolsFinder, which is used for finding
   tools in the destination
 - a ToolsUploader, which is used for uploading
   missing tools to the destination

There are two implementations of ToolsFinder
and ToolsUploader: one using Storage, and one
that uses the client API.

In cmd/juju we now use the client API unless
--local-dir is specified. --public now only
takes effect if --local-dir is specified. This
is redundant anyway, given the metadata plugins.
Merge pull request #631 from howbazaar/fix-envuser-race

Fix race in test.
Add bootstrap flag to allow failed bootstraps to keep the environment
Better warning message
Better warning message
Merge pull request #634 from wallyworld/keep-env-flag

Add bootstrap flag to allow failed bootstraps to keep the environment

Fixes: https://bugs.launchpad.net/juju-core/+bug/1362923

bootstrap now has a keep-broken flag which tells it not to cleanup after a failed bootstrap
Introduce and use FindTools provisioner API

We introduce a new FindTools API in the
provisioner facade, and move the existing
client FindTools API implementation into
the apiserver/common package. The provisioner
worker is updated to use this API instead
of going directly to provider storage (via
environs/tools.FindTools).

There are a couple of bugs already that require
this to be done, but now that we're moving tools
storage behind the API server it is imperative.

Fixes https://bugs.launchpad.net/bugs/1347984
Fixes https://bugs.launchpad.net/bugs/1304151
Merge pull request #636 from axw/provisioner-tools-api

Introduce and use FindTools provisioner API

We introduce a new FindTools API in the
provisioner facade, and move the existing
client FindTools API implementation into
the apiserver/common package. The provisioner
worker is updated to use this API instead
of going directly to provider storage (via
environs/tools.FindTools).

There are a couple of bugs already that require
this to be done, but now that we're moving tools
storage behind the API server it is imperative.

Fixes https://bugs.launchpad.net/bugs/1347984
Fixes https://bugs.launchpad.net/bugs/1304151
ActionResult refactor