NFS-11 load spike and web-{5,8,9} subsequent outage

Soft lockups on web-05, 08 and 09.

Slack discussion start: https://gitlab.slack.com/archives/C101F3796/p1507661678000242

Graphs: https://performance.gitlab.net/dashboard/db/fleet-overview?orgId=1&from=1507660738749&to=1507663081824