features/changelog: Fix for history api issue during upgrade

On failure during history changelog availability check, there
was an attempt to destory attribute (of consume thread) which
was not initialised.

Change-Id: Ica7a98ee70eb1303303884b01ef76ab71430a351
BUG: 1111169
Signed-off-by: Ajeet Jha <ajha@redhat.com>
Reviewed-on: http://review.gluster.org/8118
Reviewed-by: Kotresh HR <khiremat@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Venky Shankar <vshankar@redhat.com>
Tested-by: Venky Shankar <vshankar@redhat.com>