Install python portpicker package on Windows slaves
Install python portpicker package on Windows slaves

Change-Id: Ide0244c158b430f5d1909bc4c4a0855dfd2c0af1

bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration