Revert "TransferQueue: use a few extra buffers"

bug:7549630
bug:6876502

This reverts commit 923f222d2281bf1faac6221b3fb1298940a6d205.

Change-Id: I232a5b5b077dc1046ff2d6272876a5e5b441d42c
Only signal collection swap on true swap

bug:7484054

Change-Id: I7cb648f64f45711013996be7e2cd0dabdbd614ae