Add unit tests for local socket.

Add has_write_error flag in asocket, so it will not wait on local_socket_closing_list
to write pending packets in local_socket_close(). Although it doesn't fix any problem,
it helps to make the code more stable.
Add a missing put_apacket() in error handling.
Add a check when adding local socket in local_socket_closing_list.

Bug: 23314034

Change-Id: I75b07ba8ee59b7f277fba2fb919db63065b291be