rxrpc: Fix handling of connection failure in client call creation

If rxrpc_connect_call() fails during the creation of a client connection,
there are two bugs that we can hit that need fixing:

 (1) The call state should be moved to RXRPC_CALL_DEAD before the call
     cleanup phase is invoked.  If not, this can cause an assertion failure
     later.

 (2) call->link should be reinitialised after being deleted in
     rxrpc_new_client_call() - which otherwise leads to a failure later
     when the call cleanup attempts to delete the link again.

Signed-off-by: David Howells <dhowells@redhat.com>