api: Fix reaper functions for socket clients

api: Fix reaper functions for socket clients

Type: fix

The pub_sub_handler() stores registrations key'd with the message's client_index (which is in network-order).
The socket-client invokes the reaper function (to cleanup these registrations) using the pool index of the registration. hence the pub-sub registration is not removed.
change the socket-client to pass the network-order client_index.
This approach was chosen in preference to chaning the way the registrations are key'd since the memory-client also uses this registration, and correclty passes the client_index to the reaper.

Signed-off-by: Neale Ranns <neale@graphiant.com>
Change-Id: I6118555c8601149d05801f558e08bcc7aed4fc98