Rename camel_service_get_settings().

Rename camel_service_get_settings().

Applying lessons learned from ESourceRegistry.

Rename camel_service_get_settings() to camel_service_ref_settings()
and have it return a new reference.

When returning a pointer to a reference-counted object in a multi-
threaded environment, always increase the object's reference count
before returning so as to transfer a new reference to the caller.

Otherwise it introduces a potential race where the reference-counted
object may lose its last reference and be freed while the caller is
still using the object.  Even if the caller immediately increments
the object's reference count, it's still a potential race.

Transferring a new reference to the caller means the caller must
unreference the object when finished with it so the object will be
properly freed when it's no longer needed.