Install .rc files for ramdisk variants

Previously, we removed .rc files from ramdisk variants because init
isn't reading them. But after generic_ramdisk is introduced, we might
re-use ramdisk variant of snapuserd in recovery, and recovery will need
those .rc fiels. So install .rc files again.

Test: th
Bug: 219841787
Bug: 228893064
Change-Id: I9e6e761f4f2b3a03693567c077c3225669398b86