Support footage leftover by un-managed/moved cameras.

[CodeChief]

Use Case:
Upgrading from 2 to 3 disks in a UNVR system (requires re-format as RAID1 to RAID5 expansion is not supported), but ALSO continue to record footage. Normally this is not possible as when the cameras are moved to another Protect device (my case a UDM-Pro-SE) to continue recording they disappear from the UNVR system then this tool doesn't find the camera footage anymore (you can't save footage whilst the cameras are adopted elsewhere, even though it exists). The cameras were moved by using the "un-manage" advanced action via the Web GUI then when prompted choose the option to keep footage. As far as I remember you cannot do this on the mobile app as it only prompts to delete footage (be careful when un-managing).

Fix:
Remove logic which skips offline cameras and avoid error parsing the "stats\video\recordingStart" value in the get_camera_list.py source file. The response JSON returns "none" for "un-managed" cameras with footage.

[CodeChief]

After testing the first commit I found event download was broken by the stream download fix. Expanding the code change from a simple null workaround to a more logical conditional construction of the camera data variable appears to fix both. I've tested this on a system where the cameras were moved from and moved to (with and without cameras present, both for streams and events).

[codecov-commenter]

Codecov Report

Merging #89 (cc0c253) into master (ee40b1f) will decrease coverage by 0.12%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #89      +/-   ##
==========================================
- Coverage   53.31%   53.19%   -0.13%     
==========================================
  Files          23       23              
  Lines         724      720       -4     
==========================================
- Hits          386      383       -3     
+ Misses        338      337       -1     

Flag	Coverage Δ
unittests	53.19% <100.00%> (-0.13%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
protect_archiver/client/__init__.py	87.23% <100.00%> (ø)
protect_archiver/downloader/__init__.py	72.22% <100.00%> (ø)
protect_archiver/downloader/get_camera_list.py	90.90% <100.00%> (+3.95%)	⬆️
protect_archiver/test_client.py	100.00% <100.00%> (ø)

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[danielfernau]

Merged with a few changes. Thanks for your help, @CodeChief!