rxrpc: Fix missing locking causing hanging calls

rxrpc: Fix missing locking causing hanging calls

If a call gets aborted (e.g. because kafs saw a signal) between it being
queued for connection and the I/O thread picking up the call, the abort
will be prioritised over the connection and it will be removed from
local->new_client_calls by rxrpc_disconnect_client_call() without a lock
being held.  This may cause other calls on the list to disappear if a race
occurs.

Fix this by taking the client_call_lock when removing a call from whatever
list its ->wait_link happens to be on.

Signed-off-by: David Howells <[email protected]>
cc: [email protected]
Reported-by: Marc Dionne <[email protected]>
Fixes: 9d35d880e0e4 ("rxrpc: Move client call connection to the I/O thread")
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>