ss: Use rtnl_dump_filter in handle_netlink_request

ss: Use rtnl_dump_filter in handle_netlink_request

Replaced handling netlink messages by rtnl_dump_filter
from lib/libnetlink.c, also:

    - removed unused dump_fp arg;
    - added MAGIC_SEQ #define for 123456 seq id;
    - silently exit if ENOENT errno is caused for NETLINK_SOCK_DIAG proto
        in lib/libnetlink.c: rtnl_duml_filter_l(...) function. This fix
        was added in a3fd8e58c1787af186f5c4b234ff974544f840b6 by Eric
        for misc/ss.c

Signed-off-by: Vadim Kochan <vadim4j@gmail.com>