Changed ravenwood-junit to use module_current

Otherwise it cannot be used by mainline modules.

Test: atest --host AdServicesSharedLibrariesUnitTestsRavenwood
Test: $ANDROID_BUILD_TOP/frameworks/base/ravenwood/scripts/run-ravenwood-tests.sh
Bug: 335935200
Flag: TEST_ONLY

Change-Id: I75fc6f919ba7e45eb2fec825a2adc499a6be1b4f