net: ipc_router: Generate and relay server events under link failure

When a server unregisters/exits voluntarily, forward the REMOVE_SERVER
message generated by the peripheral to the appropriate nodes. When a link
to the peripheral fails, generate and forward the REMOVE_SERVER message
to the appropriate nodes.

Change-Id: If1e4f69ac7bbf5cd7ce48dc4f844098001fc38a4
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>