NetApp server tunneling fix.

NetApp vserver/vfiler api tunneling in concurrent requests
can cause routing request to incorrect servers in race conditions.
This fixes the api and driver for the mentioned situations.

bug 1176759

Change-Id: Id283822e4d1553daed4e6d690ec36f2edfbcf2b4
(cherry picked from commit 837df1272d43bb1a38e12d1c32183071b8294d83)
Merge "NetApp server tunneling fix." into stable/grizzly