LU-4423 ptlrpc: incorrect AT index type

LU-4423 ptlrpc: incorrect AT index type

Arnd Bergmann <arnd@arndb.de> noticed that rq_at_index is incorrectly
labelled as time_t where as it's really an integer index.

Change-Id: Id6858def627054eb87d9860ce3d98984970ed481
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/16693
Tested-by: Jenkins
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>