tests: fix a race in TestP2PwsStreamHandlerDedup

[algorandskiy]

Summary

There were couple failures in TestP2PwsStreamHandlerDedup caused by too early check on the second node - before it had a chance to handle connection closure and remove unsuccessful peer.

Additionally, there is also an attempt to fix TestCapabilities_Discovery that works on non-connected p2p hosts, manually adds peers to DHT routing table and then compares the table expected size.
Not sure what exactly it was testing (adding to routing table and checking its size looks unusual) but there is a race between capD.dht.ForceRefresh() and capD.dht.RoutingTable().Size() since as soon as it completes it prunes all non-reachable peers (and they all unreachable).
Having said that the test looks quite useless so I removed it.

Test Plan

This is a test fix.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.19%. Comparing base (e14fea6) to head (3395b0c).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6116   +/-   ##
=======================================
  Coverage   56.19%   56.19%           
=======================================
  Files         492      492           
  Lines       69783    69783           
=======================================
  Hits        39212    39212           
- Misses      27902    27904    +2     
+ Partials     2669     2667    -2     

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