[IOT-1841] Allow OT sessions to post to /pstat

[IOT-1841] Allow OT sessions to post to /pstat

Until yesterday, IOT-1831 was hiding IOT-1841, a bug in the
implementation of IOT-1801.

Change-Id: Icada8099f8c4cef9c271db8f672caa55cd63f0f5
Signed-off-by: Dan Mihai <Daniel.Mihai@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/17459
Reviewed-by: Kevin Kane <kkane@microsoft.com>
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Greg Zaverucha <gregz@microsoft.com>
Reviewed-by: Nathan Heldt-Sheller <nathan.heldt-sheller@intel.com>