Add new beholder message to track when a service gets connected, helps resolve OP-2570

[rakuy0]

The svcname field won't be available when the svc:add message goes out unless we get very lucky with a race condition. So adding a new message to indicate when the cortex gets connected to a stormsvc and we get back svcname and svcvers info.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.10 ⚠️

Comparison is base (398e9c0) 97.29% compared to head (30c8f8b) 97.19%.

❗ Current head 30c8f8b differs from pull request most recent head 950d607. Consider uploading reports for the commit 950d607 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3205      +/-   ##
==========================================
- Coverage   97.29%   97.19%   -0.10%     
==========================================
  Files         224      224              
  Lines       44896    44897       +1     
==========================================
- Hits        43681    43639      -42     
- Misses       1215     1258      +43     

Flag	Coverage Δ
linux	97.19% <100.00%> (+<0.01%)	⬆️
linux_replay	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
synapse/cortex.py	96.88% <100.00%> (-0.52%)	⬇️
synapse/lib/stormsvc.py	97.14% <100.00%> (+0.04%)	⬆️

... and 9 files with indirect coverage changes

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[vEpiphyte]

Lets add a unit test for this to the beholder test