Deactivate workers for windows

Authenticationworker and rsyslog workers are not supported on windows yet. The authentication worker will be ported on windows to add support for winrm. Rsyslog is not supported on windows yet.
Add no-op worker
Reverted cmd/jujud/unit.go
Added named pipes support

This branch replaces unix sockets with named pipes on windows.
environs/config: remove old pre 1.13 config logic
worker.Runner now treats nil error as dont-restart
Merge branch 'master' into copy-session
driveby: fix slow tests
Merge pull request #366 from fwereade/worker-finish-nil

worker.Runner now accepts nil worker returns

...and treats them as meaning "this worker has finished and does not need to be restarted".
Merge pull request #362 from davecheney/148-environs-config-cleanup

environs/config: remove old pre 1.14 config logic
Tests pass, removed @local
Logic change, create no longer errors if it exists as the exist check isn't done until write, so we try to read it first.
replicaset: rework the test to not start two mongodb replicas during the IPV6 test
Remove the error from Create as it can't fail now, and remove new file serialization structures.
Fix login deadlock
Provision new instances with version.Current

New instances were being provisioned with the agent-version from the
environ config instead of the currently running tools version. This
meant that there was a risk of new instances not running upgrade steps
if a juju upgrade occurred around the same time as the instance was
provisioned.
Remove the unneeded server uuid for now.
Merge pull request #381 from wallyworld/login-test-deadlock

Fix login deadlock

One of the login tests could deadlock. Change the test to start all N+1 attempts together, rather than N and then 1. 

Fixes lp:1347939
Merge pull request #384 from wallyworld/copy-session

Copy mongo sessions

Fixes lp:1307434 (hopefully)

Each time a mgo interaction is required, the session is copied to try and ensure the underlying socket is not stale.
Merge pull request #380 from howbazaar/configstore-no-file-until-write

Configstore no file until write

Change the ConfigStore so newly created EnvironInfo instances do not persist until they are written.

Changes the writing of the files to use a fslock instead of writing to a temporary file and renaming as a prelude to the changes coming where there will be multiple files related to a single environment connection (connection file, server file, and maybe a separate identity file)

CreateInfo now cannot return an error.

The diskinfo implementation now also separates the member storage from the persistence structure.