The test client pc gathered host candidates on every interface. On a
host with a network content filter, a STUN binding request can block
in sendto forever. The write runs inside the ICE agent taskloop, so
SetRemoteDescription and the next CreateOffer wait on that loop and
the package hits its timeout.
The test checks only SDP, so the client pc now gathers no host
candidates and neither agent sends a connectivity check.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>