Fix malformatted stream url for blink mini

[fronzbot]

Description:

Error pointed out by @cee-dee in #343

Checklist:

• Local tests with tox run successfully PR cannot be meged unless tests pass
• Changes tested locally to ensure platform still works as intended
• Tests added to verify new code works

[codecov]

Codecov Report

Merging #395 into dev will increase coverage by 1.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev     #395      +/-   ##
==========================================
+ Coverage   83.17%   84.32%   +1.14%     
==========================================
  Files           8        8              
  Lines         957      957              
==========================================
+ Hits          796      807      +11     
+ Misses        161      150      -11     

Flag	Coverage Δ
#unittests	84.32% <100.00%> (+1.14%)	⬆️

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

Impacted Files	Coverage Δ
blinkpy/camera.py	86.16% <100.00%> (+5.66%)	⬆️
blinkpy/helpers/constants.py	100.00% <100.00%> (ø)
blinkpy/api.py	63.44% <0.00%> (+2.15%)	⬆️

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