net: Local address family was not set in net_context

The address family of local endpoint address was not
set in net_context. This caused wierd issues as the
address family was always AF_UNSPEC.

Change-Id: Ibd05f9af86a8bdea3399ad20e3b84bd7d43a6415
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>