go: Fix CLI tools to not print error messages twice

[tjanez]

Previously, Execute() called nodeCommon.EarlyLogAndExit() if there was an error running rootCmd.Execute() which in turn printed the error to stderr.

The error message is printed to stdout via github.com/spf13/cobra's ExecuteC() already, so this resulted in the same error message being printed twice.

This is an expansion of f5f906b which fixed this behavior for go/oasis-test-runner/cmd.

Closes #3048.

[codecov]

Codecov Report

Merging #3230 into master will increase coverage by 0.24%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #3230      +/-   ##
==========================================
+ Coverage   67.50%   67.75%   +0.24%     
==========================================
  Files         370      370              
  Lines       36379    36379              
==========================================
+ Hits        24559    24649      +90     
+ Misses       8637     8560      -77     
+ Partials     3183     3170      -13     

Impacted Files	Coverage Δ
go/oasis-node/cmd/root.go	87.17% <0.00%> (ø)
go/consensus/tendermint/api/api.go	77.65% <0.00%> (-9.58%)	⬇️
go/worker/storage/service_external.go	57.35% <0.00%> (-2.95%)	⬇️
go/control/api/grpc.go	57.00% <0.00%> (-1.87%)	⬇️
go/runtime/host/sandbox/sandbox.go	66.54% <0.00%> (-1.49%)	⬇️
go/storage/mkvs/checkpoint/checkpointer.go	66.17% <0.00%> (-1.48%)	⬇️
go/runtime/host/protocol/connection.go	62.93% <0.00%> (-0.39%)	⬇️
go/storage/metrics.go	85.13% <0.00%> (ø)
go/storage/client/client.go	70.53% <0.00%> (ø)
go/consensus/tendermint/apps/staking/staking.go	54.67% <0.00%> (ø)
... and 23 more

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