bgpd: Allow views to 'pretend' resolve nexthops

bgpd: Allow views to 'pretend' resolve nexthops

Views are supposed to be independent tables that have no connection to
routing tables.  Since View's are 'independent' there is no way to do
'real' nexthop resolution since connected routes and interfaces are
associated with a particular table (or really vrf).  So when we have a
bgp instance assume that nexthops specified are actually valid, since we
are propagating what our neighbors are telling us.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
[cherry-picked from master 6fa1ab2eecb39b35256739f7083196d6f556f639]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>