Calibration bug fixes

[FrancaCassol]

Urgent PR to fix a bug that makes all pixels tagged as outliers. I am afraid that this will ask a new release for the onsite installation

[codecov]

Codecov Report

Base: 71.72% // Head: 71.73% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (d9cdf8c) compared to base (3a04678).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1062   +/-   ##
=======================================
  Coverage   71.72%   71.73%           
=======================================
  Files         120      120           
  Lines       11316    11320    +4     
=======================================
+ Hits         8116     8120    +4     
  Misses       3200     3200           

Impacted Files	Coverage Δ
...site/onsite_create_calibration_files_with_batch.py	31.13% <ø> (ø)
lstchain/calib/camera/pedestals.py	96.11% <100.00%> (ø)
lstchain/visualization/plot_calib.py	100.00% <100.00%> (ø)

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