LU-12199 lnet: Ensure md is detached when msg is not committed

LU-12199 lnet: Ensure md is detached when msg is not committed

It's possible for lnet_is_health_check() to return "true" when the
message has not hit the network. In this situation the message is
freed without detaching the MD. As a result, requests do not receive
their unlink events and these requests are stuck forever.

A little cleanup is included here:
 - The value of lnet_is_health_check() is only used in one place, so
   we don't need to save the result of it in a variable.
 - We don't need separate logic to detach the md when the send was
   successful. We'll fall through to the finalizing code after
   incrementing the health counters

Lustre-change: https://review.whamcloud.com/34885
Lustre-commit: b65f3a1767ae82c7f629320187b33eb8670da537

Cray-bug-id: LUS-7239
Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: I6301d491090b862d016eed3aac8afd7be8685e57
Reviewed-by: Olaf Weber <olaf.weber@hpe.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/36038
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>