Rename consumer socket fd to fd_ptr

Rename consumer socket fd to fd_ptr

By renaming this value, first the name as a better semantic and second
we are able to find every callsite that uses this variable thus making
sure we don't forget any assert or check made on it.

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>