provider/manual: don't verify bootstrap-host from inside env

StateServerInstances was attempting to verify the bootstrap
host by SSHing to itself; this fails if it does not have
authorized_keys set up appropriately. We use use-sshstorage
to detect whether we're inside the bootstrap host, and then
elide the verification if so.
provider/manual: test that Bootstrap sets use-sshstorage=false
environs/manual: revert error annotation

Leave the error alone, just log an error message.
Merge pull request #504 from axw/lp1347715-manual-stateserverinstances-noverifyinenv

provider/manual: don't verify bootstrap-host from inside env

StateServerInstances was attempting to verify the bootstrap
host by SSHing to itself; this fails if it does not have
authorized_keys set up appropriately. We use use-sshstorage
to detect whether we're inside the bootstrap host, and then
elide the verification if so.

Fixes https://bugs.launchpad.net/juju-core/+bug/1347715