core: Fix ConfigValues.GlusterAysncTasksSupport name

Renames ConfigValues attribute GlusterAysncTasksSupport
to GlusterAsyncTasksSupport.

Change-Id: Ibb72b8bd7ab184d83fe1d6c960d03027a6162456
Bug-Url: https://bugzilla.redhat.com/1112036
Signed-off-by: Martin Perina <mperina@redhat.com>