test(sudo): increase unit test coverage

[Unique-Divine]

• Continues from feat(wasm): no op handler + tests with updated contracts #1520
• Closes test: 80%+ keeper coverage for x/sudo | prio: H #1516
• Closes test: 80%+ keeper coverage for x/inflation | prio: H #1515

[codecov]

Codecov Report

Merging #1521 (1e405b4) into master (0c571c6) will increase coverage by 0.96%.
Report is 2 commits behind head on master.
The diff coverage is 70.70%.

❗ Current head 1e405b4 differs from pull request most recent head 149e575. Consider uploading reports for the commit 149e575 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1521      +/-   ##
==========================================
+ Coverage   65.34%   66.30%   +0.96%     
==========================================
  Files         161      162       +1     
  Lines       14023    13966      -57     
==========================================
+ Hits         9163     9260      +97     
+ Misses       4213     4054     -159     
- Partials      647      652       +5     

Files Changed	Coverage Δ
x/epochs/module.go	50.94% <0.00%> (ø)
x/inflation/keeper/grpc_query.go	100.00% <ø> (+85.29%)	⬆️
x/inflation/types/params.go	73.91% <ø> (ø)
x/genmsg/module.go	53.57% <53.57%> (ø)
x/genmsg/genesis.go	68.75% <68.75%> (ø)
app/app.go	64.10% <100.00%> (ø)
app/encoding.go	100.00% <100.00%> (ø)
app/keepers.go	99.06% <100.00%> (+<0.01%)	⬆️
cmd/nibid/cmd/root.go	80.82% <100.00%> (ø)
x/common/testutil/cli/network.go	59.78% <100.00%> (ø)
... and 4 more

... and 5 files with indirect coverage changes