[IoTivity Simulator]Resolved JIRA issues IOT-893 and IOT-870.

[IoTivity Simulator]Resolved JIRA issues IOT-893 and IOT-870.

IOT-893 is about the time delay after stopping the automation.
IOT-870 is about the server crash while notifying the observers.
Updated the code to allow errors when notifying the observers to be
propagated till application.

Managing thread objects using shared pointers
and detaching them for de-allocation of thread resources.

Change-Id: I06e33926a79fd241bf4089b8c4760742edab8290
Signed-off-by: G S Senthil Kumar <senthil.gs@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/4721
Reviewed-by: Radha Bhavani <radha.p@samsung.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>