linux-cp: Fix API response

linux-cp: Fix API response

* Correct endianness issue
* lip_namespace is a vector not a string
* Provide null termination to avoid unpack() failures in the client

Responses in the python API now look like:
lcp_itf_pair_details(_0=328, context=3, phy_sw_if_index=1,
  host_sw_if_index=3, vif_index=19, host_if_name='ice0',
  host_if_type=<vl_api_lcp_itf_host_type_t.LCP_API_ITF_HOST_TAP: 0>,
  namespace='dataplane')
lcp_itf_pair_details(_0=328, context=3, phy_sw_if_index=2,
  host_sw_if_index=4, vif_index=20, host_if_name='ice1',
  host_if_type=<vl_api_lcp_itf_host_type_t.LCP_API_ITF_HOST_TAP: 0>,
  namespace='dataplane')
lcp_itf_pair_details(_0=328, context=3, phy_sw_if_index=5,
  host_sw_if_index=6, vif_index=21, host_if_name='ice0.1234',
  host_if_type=<vl_api_lcp_itf_host_type_t.LCP_API_ITF_HOST_TAP: 0>,
  namespace='dataplane')

Type: fix
Signed-off-by: Pim van Pelt <pim@ipng.nl>
Change-Id: If4bf06a8b70977676ec7f5b1413cee6cc9d1714a