Improve Eureka Startup Experience

[TimHess]

Most developers expect the startup experience for service discovery to be pretty smooth and fast, even when starting Eureka and multiple services at the same time. It is mysterious for new developers and/or feels like a waste of time to have to wait a minute or more for everything to be running and for registry lookups to work. Consider alternative retry procedures (or timings) during startup and/or more helpful logging when things don't go right.

See #785 or this SO question for examples