FIX: work around issue, where ODIM startime == endtime(xarray)

[kmuehlbauer]

No description provided.

[codecov]

Codecov Report

Merging #391 into master will decrease coverage by 0.02%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #391      +/-   ##
==========================================
- Coverage   90.08%   90.05%   -0.03%     
==========================================
  Files          35       34       -1     
  Lines        5978     5950      -28     
==========================================
- Hits         5385     5358      -27     
+ Misses        593      592       -1

Flag	Coverage Δ
#wradlibtests	90.05% <66.66%> (-0.03%)	⬇️

Impacted Files	Coverage Δ
wradlib/io/xarray.py	93.4% <66.66%> (-0.25%)	⬇️
wradlib/__init__.py

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