zebra: Add error messages in places where we have a decode problem

zebra: Add error messages in places where we have a decode problem

When we receive a netlink message from the kernel we have
handler functions for when we send a netlink command, if these
return a failure ( < 0 ) then we output that we had a parse
issue.  But if all we get is:

2018-06-21T23:47:45.298156+00:00 qct-ix1-08 zebra[1484]: netlink-cmd (NS 0) filter function error

Then it is not very useful to figure out *where* the error happened.

Add more error code when in a decode path to hopefully allow us
to figure out where this message is coming from.

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