Revert of Fix a bug where if a crypto packet is spuriously retransmitted

Revert of Fix a bug where if a crypto packet is spuriously retransmitted
and thenneutered, it remains in missing_packets until the end of the
connection.

Reverted chromium cl: https://codereview.chromium.org/270213002/

Rollback of Merge internal change: 66262890.

*** Reason for rollback ***

 This appears to have caused a major QUIC loadtest regression on
 internal server.

Additionally, it's wrong in some other subtle ways, so rolling it back
and trying a new approach.

*** Original change description ***

 Fix a bug where if a crypto packet is spuriously retransmitted and then
 neutered, it remains in missing_packets until the end of the
 connection.

***

Merge internal change: 66615668

R=rch@chromium.org

[Ryan Hamilton, 2014-05-13 00:42:00]

lgtm