easy-setup: Removing redundant env configuration

easy-setup: Removing redundant env configuration

Moving global environment configuration common for all
platforms into build_common/SConscript and removing repeated
lines from service/easy-setup/*.

Bug: https://jira.iotivity.org/browse/IOT-1583
Change-Id: I76cf82bacb36d95574f5d716c01cd1d7fb7e4f5f
Signed-off-by: Pawel Winogrodzki <pawelwi@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/21325
Reviewed-by: George Nash <george.nash@intel.com>
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Mats Wichmann <mats@linux.com>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>