Remove unnecessary addresses in PF_KEY message.

MOBIKE Extensions for PF_KEY draft-schilcher-mobike-pfkey-extension-01.txt says
====================
5.  SPD Update
// snip
  SADB_X_SPDADD:
// snip
      sadb_x_ipsecrequest_reqid:

        An ID for that SA can be passed to the kernel in the
        sadb_x_ipsecrequest_reqid field.

      If tunnel mode is specified, the sadb_x_ipsecrequest structure is
      followed by two sockaddr structures that define the tunnel
      endpoint addresses.  In the case that transport mode is used, no
      additional addresses are specified.
====================
see: https://tools.ietf.org/html/draft-schilcher-mobike-pfkey-extension-01

ipsecif(4) uses transport mode, so it should not add addresses.

(knakahara)