Fix module-file name collisions

Bazel doesn't allow a module and file with the same name.

Bug: 198619163
Test: adb root; adb shell /system/bin/migrate_legacy_obb_data; adb logcat | grep obb shows "migrate_legacy_obb_data: No legacy obb data to migrate."
Change-Id: I1b5d57e6d3b2cf6f16f1d4b5039172e34be46d70