LU-12756 lnet: Introduce lnet_msg_is_response

LU-12756 lnet: Introduce lnet_msg_is_response

Implement function to determine if an lnet_msg is a response
(ACK or REPLY).

Test-Parameters: trivial
Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: I8ba2d92866f8bb2caba120d9f23218bb7761143a
Reviewed-on: https://review.whamcloud.com/36539
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@hpe.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>