features/index : Creation of indices directory as soon as brick is up.

Missing indices directory in the bricks leads to unwanted log messages.
Therefore, indices directory needs to be created as soon as the brick
comes up.
This patch results in creation of indices/xattrop directory as required.
Also includes a testcase to test the same.

Backport of http://review.gluster.org/#/c/6343/
and http://review.gluster.org/#/c/6426/

Change-Id: I2a6f48b78aa09357ed60e45b62ec5fb08f816d76
BUG: 1112111
Signed-off-by: Anuradha <atalur@redhat.com>
Reviewed-on: http://review.gluster.org/8152
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Niels de Vos <ndevos@redhat.com>