Do not pull in models into odl-mdsal-broker-local

Broker should be able to function without additional models as it
has no specific dependencies. Remove dependency on odl-mdsal-models
to allow it to load without as few models as possible.

JIRA: MDSAL-363
Change-Id: Ib230c87cbd832e16380be3b989185ac87336f30b
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>