Update juju/testing dependency

Fixes LP #1325707.
If we have a replica set, set write-majority
Test that write-majority is not set when there's no replica set
Test setting of WMode
utils: remove most of it and use juju/utils instead.

utils/ssh and utils/syslog remain in core pending removal of their
core dependencies.

This is a mechanical change.
Set J:true unconditionally for the mongo session
add juju/utils dependency
Merge remote-tracking branch 'origin/master' into 002-move-utils
fix up imports after merge
Merge branch 'master' of https://github.com/juju/juju into write-majority
delete testing/filetesting; use github.com/testing/filetesting instead
fix accidental merge issue with pull request #16

https://github.com/juju/juju/pull/16
Merge pull request #32 from johnweldon/fix-mr-16

https://github.com/juju/juju/pull/16
here's your \t
merge from trunk
Merge pull request #10 from davecheney/101-update-juju-testing-dependency

Fixes LP #1325707.
Use github.com/juju/names package

Also remove unnecessary usage of errors package when fmt was already imported.
Fix test imports
Update dependencies.tsv
fix imports test