822 forman netcdf4 lock issue

[forman]

I'm now using engine='h5netcdf' to store OPeNDAP results because the default engine='netcdf4'
causes crashes in file "netCDF4/_netCDF4.pyx" with currently used netcdf4-1.4.2 conda
package from conda-forge. This occurs whenever remote_dataset.to_netcdf() is called a
second time in the loop that iterates over all OPeNDAP urls found for a query.

Probably related to pydata/xarray#2560.
And probably fixes Cate issues #823, #822, #818, #816, #783.

[codecov-io]

Codecov Report

Merging #828 into master will decrease coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #828      +/-   ##
==========================================
- Coverage   76.75%   76.71%   -0.04%     
==========================================
  Files          82       82              
  Lines       12764    12756       -8     
==========================================
- Hits         9797     9786      -11     
- Misses       2967     2970       +3

Impacted Files	Coverage Δ
cate/ds/esa_cci_odp.py	52.48% <100%> (+0.13%)	⬆️
cate/util/web/jsonrpcmonitor.py	92.45% <0%> (-5.67%)	⬇️
cate/util/process.py	90.15% <0%> (-0.76%)	⬇️
cate/ops/coregistration.py	98.27% <0%> (+0.65%)	⬆️

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[forman]

@papesci and @dzelge this PR is for your records. I'm merging now.