Fixes lp:1339976, lp:1270466

lp:1270466
Add the following cmd to add-machine:

juju add-machine ssh:user@10.10.0.3 -i ~/myid.pub

where -i is a specific identity key used to ssh into the machine. The key is also stored in the machine for future logins.

lp:1339976
This PR also fixes a bug where cloudinit was not using the ssh client.
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Merge branch 'master' of https://github.com/juju/juju into 141-names-refactor-part-x
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Merge branch 'master' of https://github.com/juju/juju into manual-prov-key

Conflicts:
	cmd/juju/addmachine.go
	cmd/juju/addmachine_test.go
Merge branch 'master' of https://github.com/juju/juju into manual-prov-key
Merge branch 'master' of https://github.com/juju/juju into manual-prov-key
Merge branch 'master' of https://github.com/juju/juju into 141-names-refactor-part-x

Conflicts:
	state/apiserver/admin.go
	state/initialize_test.go
	state/state_test.go
Merge branch 'master' of https://github.com/juju/juju into manual-prov-key
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Merge branch '158-lets-have-less-copies-of-the-tagged-authenticator-interface' into 141-names-refactor-part-x
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Merge branch 'master' of github.com:waigani/juju into manual-prov-key
fixed apiserver/common tests
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Updated version of golxc.
Merge branch 'master' of github.com:katco-/juju