MFC: r334252

MFC: r334252
Fix the sleep event for layout recall.

The sleep for I/O completion during an NFSv4.1 pNFS layout recall used
the wrong event value and could result in the "[nfscl]" thread hung
for the mount.
This patch fixes the event to be the correct.
This bug will only affect NFSv4.1 pnfs mounts and only when the server
does a layout recall callback, so it won't affect many. Without the patch,
a mount without the "pnfs" option will avoid the problem.
Found during testing of the pNFS server.

git-svn-id: svn://svn.freebsd.org/base/stable/10@334635 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f