staging: lustre: lnet: Do not drop message when shutting down LNet
There is a case in lnet_parse() where we discover that LNet
is shutting down but we continue to use the NI when we drop the
message and end up calling ko2iblnd_check_send_locked() which tries to
allocate from the Tx pool which has been cleaned up already.
This triggers a NULL pointer dereference.
This fix just returns from lnet_parse() when we disover LNet is
shutting down.