fix opentracing log_kv() arg

[vetinari]

must be a dict, not a set, otherwise we'd get something like

   File "/usr/local/lib/python3.6/dist-packages/opentracing-1.3.0-py3.6.egg/opentracing/span.py", line 211, in __exit__
     self.finish()
   File "/usr/local/lib/python3.6/dist-packages/basictracer/span.py", line 56, in finish
     self._tracer.record(self)
   File "/usr/local/lib/python3.6/dist-packages/basictracer/tracer.py", line 100, in record
     self.recorder.record_span(span)
   File "/usr/local/lib/python3.6/dist-packages/lightstep/recorder.py", line 184, in record_span
     event = log.key_values.get('event') or ''
 AttributeError: 'set' object has no attribute 'get'

[codecov[bot]]

Codecov Report

Merging #89 into master will not change coverage. The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #89   +/-   ##
=======================================
  Coverage   77.97%   77.97%           
=======================================
  Files          18       18           
  Lines        1158     1158           
=======================================
  Hits          903      903           
  Misses        255      255

Impacted Files	Coverage Δ
zmon_cli/client.py	97.91% <100%> (ø)	:arrow_up:

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[vetinari]

:+1:

[rajatparida86]

👍