Properly size response buffer in ifc_act_on_address

Currently, any netlink error reported in ifc_act_on_address is
reported as EINVAL, because the receive buffer is too short and
the NLMSG_OK check fails on it.

Make the buffer long enough so the function can return the
correct netlink error to the caller.

Test: new test coverage in other CL in this topic
Change-Id: Ica752db834a0fd614312b800d88721826be08d56