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.
add juju/utils dependency
Merge remote-tracking branch 'origin/master' into 002-move-utils
fix up imports after merge
Merge remote-tracking branch 'origin/master' into 002-move-utils

Conflicts:
	dependencies.tsv
gofmt
fix dependency tests
Merge pull request #28 from rogpeppe/002-move-utils

utils/ssh and utils/syslog remain in core pending removal of their
core dependencies.

This is a mechanical change.