lsfd: support AF_VSOCK sockets

lsfd: support AF_VSOCK sockets

Example output:

    # ./lsfd -p 121067 -Q "TYPE == 'AF_VSOCK'"
    COMMAND       PID USER ASSOC  XMODE     TYPE SOURCE MNTID    INODE NAME
    test_mkfds 121067 root     4 rw---- AF_VSOCK sockfs    10 39400798 state=listen type=stream laddr=local:12345
    test_mkfds 121067 root     5 rw---- AF_VSOCK sockfs    10 39400799 state=established type=stream laddr=local:23456 raddr=local:12345
    test_mkfds 121067 root     6 rw---- AF_VSOCK sockfs    10 39400800 state=established type=stream laddr=local:12345 raddr=local:23456

Signed-off-by: Masatake YAMATO <yamato@redhat.com>