[IOT-1611] Memory corruption in OCSetAttribute

[IOT-1611] Memory corruption in OCSetAttribute

Fix memory corruption bugs in OCSetAttribute introduced by
https://gerrit.iotivity.org/gerrit/#/c/14377/ which left pointers to
freed memory in the attribute list, which was then later used.

Change-Id: Ib776d4bd14aab7b39c74188246005628fbe18ecf
Signed-off-by: Dave Thaler <dthaler@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/14873
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>
Reviewed-by: Habib Virji <habib.virji@samsung.com>
Reviewed-by: Ziran Sun <ziran.sun@samsung.com>