Removed OpFlex domain scoping.

There will only be a single OpFlex domain, so the domain
is brought out to a top-level configuration item (and is
no longer a list of domains) and brings the Discovery Definitions
back to the top level.

Change-Id: I688335d5b6b6c6980fcec40480d5e9ba4809faf1
Signed-off-by: Thomas Bachman <tbachman@yahoo.com>