Fix a flaky turnport test failure
Fix a flaky turnport test failure

The connection was deleted asynchronously, so need to use EXPECT_TRUE_WAIT.

BUG=
TBR=pthatcher@webrtc.org

Review URL: https://codereview.webrtc.org/1567433002 .

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#11153}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: b6802749f1c87e10b2442ecf3e75ba7b8ff45188

Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc