Fix port string to uint16 parsing

[taylanisikdemir]

What changed?
Port strings are parsed to uint16 in ringpop library. Ports can be numbered from 0 to 65535 which is uint16 range.
Currently the parsing is done using ParseInt instead of ParseUint which fails to parse ports greater than 32767.

Why?
Avoid bugs for port numbers > 32767.

How did you test it?
Unit test.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.13%. Comparing base (78eb2c8) to head (011c1df).
Report is 1 commits behind head on master.

Additional details and impacted files

Files with missing lines	Coverage Δ
common/peerprovider/ringpopprovider/provider.go	3.90% <100.00%> (+3.90%)	⬆️

... and 4 files with indirect coverage changes

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