ensure we always have publisher/caller information

[meejah]

See also crossbario/autobahn-python#1393 (which is needed to make this work).

[codecov-commenter]

Codecov Report

Merging #1778 into master will increase coverage by 0.01%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master    #1778      +/-   ##
==========================================
+ Coverage   32.25%   32.27%   +0.01%     
==========================================
  Files          81       81              
  Lines       13919    13936      +17     
  Branches     2465     2466       +1     
==========================================
+ Hits         4490     4498       +8     
- Misses       9037     9048      +11     
+ Partials      392      390       -2     

Impacted Files	Coverage Δ
crossbar/worker/rlink.py	18.30% <20.00%> (+0.54%)	⬆️
crossbar/router/broker.py	28.77% <100.00%> (+0.14%)	⬆️
crossbar/router/dealer.py	35.43% <100.00%> (+0.10%)	⬆️
crossbar/webservice/base.py	29.10% <0.00%> (-0.21%)	⬇️
crossbar/bridge/mqtt/wamp.py	30.44% <0.00%> (ø)

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[oberstet]

so this is just a stop-gap "solution", until we have rectified crossbario/autobahn-python#1392, right?

because all of sessionid, authid and authrole MUST (well, should, because of of above unfixed issue) always be available to rlinks