Fix flaky tests by require root for minadbd_tests

minadbd tests require access to /dev/fuse, therefore needs to run as
root. This test has been flaky because root preparetor wasn't specified.

Bug: 165604640
Test: atest MinadbdServicesTest
Change-Id: I6ee1e2deede4352e28aad79c436ec5974e7d64f6

minadbd/Android.bp

@@ -135,4 +135,5 @@ cc_test {
     test_suites: [
         "device-tests",
     ],
+    require_root: true,
 }

minadbd/AndroidTest.xml

@@ -18,6 +18,7 @@
         <option name="cleanup" value="true" />
         <option name="push" value="minadbd_test->/data/local/tmp/minadbd_test" />
     </target_preparer>
+    <target_preparer class="com.android.tradefed.targetprep.RootTargetPreparer"/>
     <option name="test-suite-tag" value="apct" />
     <test class="com.android.tradefed.testtype.GTest" >
         <option name="native-test-device-path" value="/data/local/tmp" />