tests/webrtc: fix tests for no libnice

webrtcbin will fail the state change to READY when libnice elements are
not available.
3 jobs for webrtc-test-fixes in 4 minutes and 4 seconds
Status Name Job ID Coverage
  Preparation
passed manifest #49585

00:00:21

 
  Build
passed build fedora x86_64 #49586

00:01:23

 
  Full Builds
passed build android arm64 api28 #49587

00:02:18