zebra: Modify code so that dplane is responsible for indicating success/fail of install

zebra: Modify code so that dplane is responsible for indicating success/fail of install

We have several route types KERNEL and CONNECT that are handled via special
case in the code.  This was causing a lot of work keeping the two different
classes of route types as special(SYSTEM OR NOT).  Put the dplane
in charge of the code that sets the bits for signalling route install/failure.

This greatly simplifies the code calling path and makes all route types
be handled exactly the same.  Additionaly code that we want to run
post data plane install can just work as per normal then, instead
of having to know we need to run it when we have a special type
of route.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com.