Fix bug that prevents "https://" netCDF files from being read

[davidhassell]

Fixes #268

[codecov]

Codecov Report

Merging #269 (8860191) into main (142accf) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #269      +/-   ##
==========================================
+ Coverage   87.35%   87.36%   +0.02%     
==========================================
  Files         125      125              
  Lines       12887    12887              
==========================================
+ Hits        11256    11258       +2     
+ Misses       1631     1629       -2     

Flag	Coverage Δ
unittests	87.36% <100.00%> (+0.02%)	⬆️

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Files Changed	Coverage Δ
cfdm/read_write/netcdf/netcdfread.py	83.64% <100.00%> (+0.05%)	⬆️

... and 1 file with indirect coverage changes

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[bewithankit]

Also checked with another OPeNDAP URL and it works:

>>> import cfdm
>>> j = cfdm.read('https://dapds00.nci.org.au/thredds/dodsC/zv2/agcd/v2-0-1/precip/total/r005/01month/agcd_v2-0-1_precip_total_r005_monthly_1900.nc')
[<Field: lwe_thickness_of_precipitation_amount(time(12), latitude(691), longitude(886)) mm>]

Thank you David. Merge when ready!