add stop API of base stack in android.

add stop API of base stack in android.

since some user application want to use IoTivity more dynamically.
stop API of IoTivity should be provided effeciently.

Change-Id: Ie9ebb874b9b1d49703d5023a972cff5c630acaf3
Signed-off-by: jihwan.seo <jihwan.seo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13649
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Larry Sachs <larry.j.sachs@intel.com>
Reviewed-by: Jaehong Jo <jaehong.jo@samsung.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>