Update expectations to rspec v3 `expect `format.

Signed-off-by: Caleb Miles <cmiles@pivotallabs.com>
Bosh::Director::DeploymentPlan::Notifier to send start/end/error events.

[#77383434]

Signed-off-by: Caleb Miles <cmiles@pivotallabs.com>
Emit deployment-related events during update deployment.

- added event: begin update deployment
- added event: finish update deployment
- added event: error during update deployment
- also cleaned up specs:
  - pulled instance variables into `let` blocks
  - moved common setup into a context

[#77383434]

Signed-off-by: Caleb Miles <cmiles@pivotallabs.com>
Integration test for update deployment events.

- ensure the Bosh HM logs an alert when it sees start and stop events

[#77383434]

Signed-off-by: Caleb Miles <cmiles@pivotallabs.com>