Revert "Revert "SharedMemory: break Cleaner reference cycle.""

This reverts commit b16411f83aee0847fec77d79fb4e98b2e3fa8828.

The original change was correct, and the revert re-introduced an
FD leak.

Test: make
Bug: 197500807
Change-Id: Id5118e2b21fa4b7a7198edfe9541f755fd581752
1 file changed