Revert "Don't try to ramp up TCP send buffer sizes #4489"

This reverts commit e78a2a7d29d7a94df9d7d43d91b4feb210bf7a5a.
Add some comments to help understand memory model w/ DACLS. #4467
Fix bug setting socket buffer sizes on newer linux kernels. #4489

The problem was on the 3.14 kernel, the kernel doesn't support
setting the send buffer less than about 4k bytes, so our initial
attempts to set it to 1k and 2k both result in setting it to 4k.
Condor notices that the size isn't going up, and stops trying
well short of the requested size.
Add COLLECTOR_SOCKET_BUFSIZE to param table. #4489

Also remove NEGOTIATOR_SOCKET_BUFSIZE from param table, which was
never being used.