Start with dummy video audio and open stream and replace tracks on the fly

[mekya]

ant-media/Ant-Media-Server#5392

[codecov]

Codecov Report

Patch coverage: 77.01% and project coverage change: +49.25% 🎉

Comparison is base (c1e8ea3) 0.00% compared to head (fbe8808) 49.25%.

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #395       +/-   ##
===========================================
+ Coverage        0   49.25%   +49.25%     
===========================================
  Files           0        7        +7     
  Lines           0     1752     +1752     
===========================================
+ Hits            0      863      +863     
- Misses          0      889      +889     

Files Changed	Coverage Δ
src/main/webapp/js/media_manager.js	42.12% <76.47%> (ø)
src/main/webapp/js/webrtc_adaptor.js	43.72% <100.00%> (ø)

... and 5 files with indirect coverage changes

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