Switch to system user before running incident module.

Module tests features that only work for user 0 (ErrorTest verifies
DropBoxManager which only broadcasts to user 0).
Use target provider to switch to user 0 before the module execution,
and switch back to whatever user we were in after we're done.

bug: 123154921
Test: cts-tradefed run cts-dev -m CtsIncidentHostTestCases
Change-Id: I58c228bbbdfe0c623ee92f5deaa53a80ea79138e
diff --git a/hostsidetests/incident/AndroidTest.xml b/hostsidetests/incident/AndroidTest.xml
index 641b516..18a73fa 100644
--- a/hostsidetests/incident/AndroidTest.xml
+++ b/hostsidetests/incident/AndroidTest.xml
@@ -16,6 +16,9 @@
 <configuration description="Config for CTS Incident host test cases">
     <option name="test-suite-tag" value="cts" />
     <option name="config-descriptor:metadata" key="component" value="metrics" />
+    <target_preparer class="com.android.tradefed.targetprep.SwitchUserTargetPreparer">
+        <option name="user-type" value="system" />
+    </target_preparer>
     <test class="com.android.compatibility.common.tradefed.testtype.JarHostTest" >
         <option name="jar" value="CtsIncidentHostTestCases.jar" />
     </test>