Windows: single-threaded unit test run
Windows: single-threaded unit test run

Serialize the tests, because otherwise investigation of failures is
too difficult. For an example of puzzling failure, see:
https://build.iotivity.org/ci/job/iotivity-verify-windows-x86-vs2015/1495/

Change-Id: I90b836b4c4c6587de108de32d761f99fb3073819
Signed-off-by: Dan Mihai <ba8e1833495515b49ded9e20cae80a8129155aa9@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/20061
Tested-by: jenkins-iotivity <d95b56ce41a2e1ac4cecdd398defd7414407cc08@iotivity.org>

rzr/iotivity,iotivity/iotivity,iotivity/iotivity,iotivity/iotivity,rzr/iotivity,iotivity/iotivity,rzr/iotivity,rzr/iotivity,iotivity/iotivity,iotivity/iotivity,rzr/iotivity,rzr/iotivity,rzr/iotivity,iotivity/iotivity,iotivity/iotivity