fix linter errors thrown by `unconvert`, `goconst`, and `nakedret` (#3960)
* Remove unnecessary type conversions
* Consolidate repeated strings into consts
* Clothe return statements
* Update blockchain/v1/reactor_fsm_test.go
Co-Authored-By: Anton Kaliaev <anton.kalyaev@gmail.com>
This PR repairs linter errors seen when running the following commands:
golangci-lint run --no-config --disable-all=true --enable=unconvert
golangci-lint run --no-config --disable-all=true --enable=goconst
golangci-lint run --no-config --disable-all=true --enable=nakedret
Contributes to #3262