Fix FinalModifierException due to BindingToNormalizedNodeCodec final

Fix FinalModifierException due to BindingToNormalizedNodeCodec final

The BindingToNormalizedNodeCodec class is final which prevents blueprint from
being able to create a proxy instance when advertising as a service. This is
is OK as it will use the actual instance but it logs an exception:

2016-08-11 23:03:18,215 | INFO  | rint Extender: 2 | ServiceRecipe
| 15 - org.apache.aries.blueprint.core - 1.6.1 | Unable to create a
proxy object for the service .component-2 defined in bundle
org.opendaylight.controller.sal-binding-broker-impl/1.5.0.SNAPSHOT with
id. Returning the original object instead.
org.apache.aries.proxy.FinalModifierException: The class
org.opendaylight.controller.md.sal.binding.impl.BindingToNormalizedNodeCodec
is final.
	at
org.apache.aries.proxy.impl.gen.ProxySubclassGenerator.scanForFinalModifiers(ProxySubclassGenerator.java:330)[12:org.apache.aries.proxy.impl:1.0.5]

Although it's logged at INFO level we should avoid it.

Changing BindingToNormalizedNodeCodec to non-final fixes the exception however it causes
an error when it tries to create the proxy b/c some methods are final. To avoid this, weneed to avoid the proxy creation altogether so I added a method to
BindingToNormalizedNodeCodecFactory to advertise the OSGi service instead of using
the blueprint <service> element.

Note: it's not good practice to advertise a service with the actual class but it's
needed with BindingToNormalizedNodeCodec for backwards compatibility with CSS modules
that inject the BindingToNormalizedNodeCodec instance and not its interfaces. The
BindingToNormalizedNodeCodec CSS service identity is deprecated and will/should go away in the future.

Change-Id: I96b6cb8b030de39808de17142d79f8bbd09bf735
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>