INFINITY-3491/3495 Fix invalid reservation handling, add hello-world examples

[nickbp]

Fixes:

• When in multi-service mode, we would previously clean reservations that lacked a service name label. Instead, just complain and leave them be.
• CuratorLocker had again started getting invoked after other access had already happened. Fix the problem once and for all by moving locking immediately before building the CuratorPersister object itself.
• Other fixes from INFINITY-3472/3475 Finish first draft of multi-service support #2460

New:

• Updates hello-world to include a reference implementation of running a 'dynamic' multi-service scheduler, as well as a 'static' multi-service scheduler, in addition to the current single-service options. Dynamic mode is run when no yaml files are provided, while static is run when multiple (comma or space-separated) yaml files are provided. Next is to add integration tests against this implementation (JIRA filed)

[gabrielhartmann]

add another field yamls for this.