libnetlink: Add variant of rtnl_talk that does not display RTNETLINK answers error

libnetlink: Add variant of rtnl_talk that does not display RTNETLINK answers error

iplink_vrf has 2 functions used to validate a user given device name is
a VRF device and to return the table id. If the user string is not a
device name ip commands with a vrf keyword show a confusing error
message: "RTNETLINK answers: No such device".

Add a variant of rtnl_talk that does not display the "RTNETLINK answers"
message and update iplink_vrf to use it.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>