Fix render with panel not loading extension dirs correctly

[govinda18]

Fixes #4082

[codecov]

Codecov Report

Merging #4083 (0bf3713) into master (a1fc86d) will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #4083   +/-   ##
=======================================
  Coverage   83.58%   83.58%           
=======================================
  Files         223      223           
  Lines       33243    33244    +1     
=======================================
+ Hits        27785    27787    +2     
+ Misses       5458     5457    -1     

Flag	Coverage Δ
ui-tests	37.56% <0.00%> (-0.02%)	⬇️
unitexamples-tests	74.66% <0.00%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
panel/io/jupyter_server_extension.py	0.00% <0.00%> (ø)
panel/io/state.py	70.00% <0.00%> (ø)
panel/tests/command/test_serve.py	85.36% <0.00%> (+2.43%)	⬆️

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