Updated with Valgrind memory leak fixes for Notification Provider and consumer.

Updated with Valgrind memory leak fixes for Notification Provider and consumer.
Updated NS sample App to allow/deny consumer subscription.

Patch 2 : updated valgrind fixes and updated review comments
patch 3 : rebased the code.
patch 4 : resolved merge conflicts

Change-Id: Icdcc0b71fb865fbbb5dd472045e71cef2689d2c6
Signed-off-by: Abitha Shankar <abitha.s@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13453
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>