RecreateWebRtcStream was checking the "sending_" flag, but wasn't
checking rtp_parameters_.encodings[0].active. As a result, if an
application calls "RtpSender.setParameters(inactive_params)" then later
the stream is recreated due to some change in SDP parameters, the stream
would incorrectly start sending.
R=pthatcher@webrtc.org, skvlad@webrtc.org
Review URL: https://codereview.webrtc.org/2246313002 .
Cr-Commit-Position: refs/heads/master@{#14116}