Refactor IpRuleCommand to take more arguments

Refactor IpRuleCommand to take more arguments

The iproute2 rule command takes more arguments than the ones supported
by this wrapper.  Particularly, for address scopes, we're interested
in iif and fwmark.  Instead of adding these piecemeal, this change
makes the wrapper flexible to pass any of them using kwargs.

Callers of add / delete are updated to pass keyword arguments for
table and priority since they are no longer required positional
arguments.  This looks better anyway.

Change-Id: Ia93b086b787c34bd560961cb84e4a003cf359e7e
Partially-Implements: blueprint address-scopes