go staking: add isTransferPermitted tests

[pro-wh]

it was desired that we have tests for this transfer permissions engine

[codecov]

Codecov Report

Merging #2503 into master will increase coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2503      +/-   ##
==========================================
+ Coverage   67.02%   67.12%   +0.09%     
==========================================
  Files         324      324              
  Lines       29887    29887              
==========================================
+ Hits        20033    20061      +28     
+ Misses       7377     7351      -26     
+ Partials     2477     2475       -2

Impacted Files	Coverage Δ
go/worker/storage/service_external.go	57.14% <0%> (-6.35%)	⬇️
go/common/cbor/codec.go	64.7% <0%> (-5.89%)	⬇️
go/worker/common/p2p/p2p.go	65.31% <0%> (-3.16%)	⬇️
go/roothash/api/commitment/pool.go	70.5% <0%> (-0.59%)	⬇️
go/consensus/api/grpc.go	57.02% <0%> (ø)	⬆️
go/consensus/tendermint/tendermint.go	63.07% <0%> (ø)	⬆️
go/worker/merge/committee/node.go	75.36% <0%> (ø)	⬆️
go/consensus/tendermint/abci/mux.go	68.11% <0%> (+0.72%)	⬆️
go/worker/common/committee/group.go	81.78% <0%> (+0.74%)	⬆️
go/storage/api/grpc.go	69.86% <0%> (+1.36%)	⬆️
... and 4 more

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