Memoize app_event_repository instance

  * this is currently needed for testing

Signed-off-by: Aram Price <aprice@pivotallabs.com>
Move app.update loggregator message to AppEventRepository

Signed-off-by: Aram Price <aprice@pivotallabs.com>
Move loggregator emit message on app create to AppEventRepository

Signed-off-by: Aram Price <aprice@pivotallabs.com>
Move loggregator emit message on app delete to AppEventRepository

Signed-off-by: Aram Price <aprice@pivotallabs.com>
Emit loggregator message on app exit

[#61987212]

Signed-off-by: Aram Price <aprice@pivotallabs.com>