Removed unused fakeRestart func
cmd/jujud: retry upgrades on failure

Given that we currently have no way of rolling back upgrades it's
worth retrying upgrades in case of transient errors. Logging around
upgrades has been improved a bit as well.

Future changes will improve the handling of upgrade error reporting
further (via agent status).
Merge pull request #322 from mjs/retry-upgrade-steps

cmd/jujud: retry upgrades on failure

Given that we currently have no way of rolling back upgrades it's worth retrying upgrades in case of transient errors. Logging around upgrades has been improved a bit as well.

Future changes will improve the handling of upgrade error reporting further (via agent status).