Make sure send and receive deltas are positive for remote estimated probe clusters.

BUG=b/65531353

Review-Url: https://codereview.webrtc.org/3005393002
Cr-Original-Commit-Position: refs/heads/master@{#19796}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 0c011d9499deb10b3a3d15dd7a3c52b07babeacd