[SSM] Fix SSM Sample App to handle invalid input for app menu (IOT-290)

[SSM] Fix SSM Sample App to handle invalid input for app menu (IOT-290)

Modify SSM Linux Sample App to to prevent unexpected input values

Change-Id: Ic9de6e894a44a903f02d60f6eeaf0fa9035e0e5a
Signed-off-by: Minji Park <minjii.park@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/315
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
(cherry picked from commit d37ac7328d1f6bf0fc8da65aac9af8b0edcdd904)
Reviewed-on: https://gerrit.iotivity.org/gerrit/384
Reviewed-by: Sudarshan Prasad <sudarshan.prasad@intel.com>