build: Use mbedtls in secured mode regardless WITH_TCP

build: Use mbedtls in secured mode regardless WITH_TCP

As mbedtls comes now in SECURED mode (even without TCP),
 project is not buildable anymore
 since this change:
https://gerrit.iotivity.org/gerrit/#/c/14883/21/resource/csdk/connectivity/src/SConscript

Ported from 1.2-rel branch to master

Conflicts:
	resource/csdk/stack/samples/linux/OCSample/SConscript
	service/easy-setup/mediator/richsdk/unittests/SConscript
	service/resource-encapsulation/src/common/SConscript
	service/resource-encapsulation/src/serverBuilder/SConscript
	service/scene-manager/unittests/SConscript

Bug: https://jira.iotivity.org/browse/IOT-1622
Change-Id: I202b0e8a9aea6f0675e966ae72325a1ed2cf13f9
Signed-off-by: Philippe Coval <philippe.coval@osg.samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/15809
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: George Nash <george.nash@intel.com>
Reviewed-by: Nivedita Singhvi <niveditasinghvi@gmail.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/16931
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Kevin Kane <kkane@microsoft.com>
Reviewed-by: Ziran Sun <ziran.sun@samsung.com>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>