ANDROID: kselftests: Use tests-dir in kselftest script

Replace usage of `--extra-file testsdir` with `--tests-dir` to prevent
folder from being cleaned up unintentionally.

Bug: 291147200
Change-Id: I535780afb272dd3494756c61a8b474157ce94b9b
Signed-off-by: Edward Liaw <edliaw@google.com>

tools/testing/android/bin/kselftest.sh

@@ -68,7 +68,7 @@ echo "Building selftests..."
 $BAZEL build //common:kselftest_tests_x86_64
 
 $TRADEFED run commandAndExit template/local_min --template:map test=suite/test_mapping_suite \
---include-filter selftests --extra-file testsdir=$TESTSDIR --primary-abi-only
+--include-filter selftests --tests-dir=$TESTSDIR --primary-abi-only
 
 if $LAUNCH_CVD && $KILL_CVD; then
     echo "Test finished. Deleting cvd..."