performance/io-cache: propagate errors while unwinding frame in
                      read path.

Change-Id: Ieb5d592a987e8681d5ec019da309f75e3b207580
BUG: 858242
Signed-off-by: Raghavendra G <raghavendra@gluster.com>
Reviewed-on: http://review.gluster.org/4204
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>