rdma: Provide and reuse filter functions

rdma: Provide and reuse filter functions

Globally replace all filter function in safer variants of those
is_filtered functions, which take into account the availability/lack
of netlink attributes.

Such conversion allowed to fix a number of places in the code, where
the previous implementation didn't honor filter requests if netlink
attribute wasn't present.

Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David Ahern <dsahern@gmail.com>