object-storage: provide more common cfg defaults

Provide more common configuration defaults, as seen and recommended across
many large customer installations, as well as provide some guidance on how to
set the parameters.

See BZ 904629 (https://bugzilla.redhat.com/show_bug.cgi?id=904629).

Change-Id: Id9f20aafd75f2a0b589c67654dce87534bf80c33
BUG: 904629
Signed-off-by: Mohammed Junaid <junaid@redhat.com>
Reviewed-on: http://review.gluster.org/4789
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>