LU-5829 obdclass: remove unnecessary EXPORT_SYMBOL

LU-5829 obdclass: remove unnecessary EXPORT_SYMBOL

A lot of symbols don't need to be exported at all because they are
only used in the module they belong to.

Removed now unused function cat_cancel_cb() and fixed 3 comments in
test code mentioning this function.

Signed-off-by: frank zago <fzago@cray.com>
Change-Id: Ia0fa1e8e65f197235c04997f56b49d8fd87d4fd6
Reviewed-on: http://review.whamcloud.com/13323
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>