Fix CtsOsTestCases to run on user builds.

DeviceSetup preparer by default tries to set properties
that require `adb root`. We must skip the step for CTS.

Bug: 160439034
Bug: 160659153
Test: CtsOsTestCases
Change-Id: Ieb4d4351de1ce5f420de516a3b98048c5c765619
1 file changed