bgpd: fix for leaked struct bgp_adj_[in|out] on peer shutdown

bgpd: fix for leaked struct bgp_adj_[in|out] on peer shutdown

    If a peer with soft-reconfiguration configured is cleared, the
function bgp_clear_route_table() doesn't free the bgp_adj_in and bgp_adj_out
structures of route nodes that for some reason, ej. denied by a filter,
don't have routes attached "rn->info == NULL".

Signed-off-by: Jorge Boncompte [DTI2] <jorge@dti2.net>
Reviewed-by: Leonid Rosenboim <Leonid.Rosenboim@windriver.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>