Use hyphen to escape package name.

We used underscore which is a valid character in Java identifier (though
rarely used). Use hyphen instead to avoid conflict.

Bug: 159243914
Test: atest LaunchParamsPersisterTests
Test: Old records can be restored.
Test: Old files don't exist anymore.
Change-Id: Ia1f01653e43b01fb98cb8baf027f46e1778f9608