Fix connectSome test util

[twoeths]

Motivation
In connectSome() function, it does not check for duplicate, a peer may connect to less than the specified "num" peers

Description
Maintain candidatePeers array and do the random on its key.

Close #240

[codecov-commenter]

Codecov Report

Merging #241 (da7d51a) into master (dc29113) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #241      +/-   ##
==========================================
- Coverage   80.31%   80.27%   -0.04%     
==========================================
  Files          24       24              
  Lines        7661     7661              
  Branches      818      818              
==========================================
- Hits         6153     6150       -3     
- Misses       1508     1511       +3     

Impacted Files	Coverage Δ
ts/score/peer-score.ts	92.09% <0.00%> (-0.50%)	⬇️

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[dapplion]

Tagging for review @achingbrain if available

[dapplion]

I haven't reviewed the algorithm correctness, otherwise LGTM