Add DocumentsUITests.apk to MTS to get coverage data.

Bug:143778863
Test: m mts
Change-Id: Id905a2540a3e4bcbd93e68e80c4c2f3e48651cf8
diff --git a/tests/Android.bp b/tests/Android.bp
index 92c578d..15aac38 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -87,6 +87,7 @@
 
     test_suites: [
         "device-tests",
+        "mts",
     ],
 
     platform_apis: true,
diff --git a/tests/AndroidTest.xml b/tests/AndroidTest.xml
index 7893150..7874118 100644
--- a/tests/AndroidTest.xml
+++ b/tests/AndroidTest.xml
@@ -14,7 +14,7 @@
      limitations under the License.
 -->
 <configuration description="Runs Tests for DocumentsUI.">
-    <target_preparer class="com.android.tradefed.targetprep.TestAppInstallSetup">
+    <target_preparer class="com.android.tradefed.targetprep.suite.SuiteApkInstaller">
         <option name="test-file-name" value="DocumentsUITests.apk" />
     </target_preparer>