disable BT transport in iotivity.spec by default.

disable BT transport in iotivity.spec by default.

since BT is not mandatory transport type,
it causes a waste of resource(memory).
thru, it is better to disable.

Change-Id: Ic2eabf0166383f7d391197a1fd0a4ac1ed6d185d
Signed-off-by: jihwan.seo <jihwan.seo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/16419
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>
Reviewed-by: Jaehong Jo <jaehong.jo@samsung.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>