LU-12440 lnet: Misleading error from lnet_is_health_check

LU-12440 lnet: Misleading error from lnet_is_health_check

In the case of sending to 0@lo we never set msg_txpeer nor
msg_rxpeer. This results in failing this lnet_is_health_check
condition and a misleading error message. The condition is only an
error the msg status is non-zero.

An additional case where we can have msg_rx_committed, but not
msg_rxpeer is for optimized GETs. In this case we allocate a reply
message but do not set msg_rxpeer.  We cannot perform further health
checking on this message, but it is not an error condition.

Test-parameters: trivial
Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: I56b1f2aa98945939e4b7ae8266de66cf27f35869
Reviewed-on: https://review.whamcloud.com/35235
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Reviewed-by: Alexandr Boyko <c17825@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>