catchpointdump: set genesis proto version

[algorandskiy]

Summary

Catchpointdump does not have access to a ledger and it does not know
which consensus params is to use as genesis state on rewards calculation
that can lead to division by zero panic.

This PR sets a hardcoded value to ConsensusCurrentVersion.

Additionally, let net subcommand to return non-zero exit code
to indicate nothing was downloaded.
To do that I converted it to cobra.RunE-style method in order to use
a standard cobra's error reporting and exit code setter.

Test Plan

Tested manually

[codecov-commenter]

Codecov Report

Merging #3596 (cfc718e) into master (f00b072) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3596      +/-   ##
==========================================
- Coverage   47.59%   47.58%   -0.01%     
==========================================
  Files         370      370              
  Lines       60093    60093              
==========================================
- Hits        28601    28595       -6     
- Misses      28183    28185       +2     
- Partials     3309     3313       +4     

Impacted Files	Coverage Δ
ledger/roundlru.go	90.56% <0.00%> (-5.67%)	⬇️
agreement/cryptoVerifier.go	75.17% <0.00%> (-2.13%)	⬇️
agreement/proposalManager.go	96.07% <0.00%> (-1.97%)	⬇️
catchup/peerSelector.go	98.95% <0.00%> (-1.05%)	⬇️
network/wsNetwork.go	62.79% <0.00%> (-0.20%)	⬇️
data/transactions/verify/txn.go	44.44% <0.00%> (ø)
network/wsPeer.go	68.33% <0.00%> (+0.27%)	⬆️
ledger/blockqueue.go	85.05% <0.00%> (+2.87%)	⬆️

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