modify the preprocessor to stop the thread in ipadapter

modify the preprocessor to stop the thread in ipadapter

In case I use a ndk-build for android sample build,
the MULTI_THREAD is not defined.
because preprocessor was defined within Sconscript.
so I modified the code to stop the send thread.

Change-Id: I732fad2120fe243b6b976230aa395fdbb385dda1
Signed-off-by: hyuna0213.jo <hyuna0213.jo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/1588
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Naga Ashok Jampani <jn.ashok@samsung.com>
Reviewed-by: Erich Keane <erich.keane@intel.com>