LU-15791 tests: Get health before removing drop rules

LU-15791 tests: Get health before removing drop rules

lnet_health_post() can race with recovery pings, so we should
wait to delete the drop rules until after we've gathered the
health and resend values.

Test-Parameters: trivial testlist=sanity-lnet
Fixes: 79ab053562 ("LU-13569 lnet: Deprecate lnet_recovery_interval")
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: Ia7595e015809f796cafcc40382d98ab66a708a49
Reviewed-on: https://review.whamcloud.com/47998
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>