Review unit test coverage of modules

[LucasIsasmendi]

Parent #1169

• account: incomplete test
• blocks: all test are pending (Add unit test coverage for modules blocks #1711)
• cache: incomplete test
• dapps: all test are pending
• delegates: most test are pending
• loader: most test are pending (refactor code base due to nested functions)
• multisignature: all tests are pending (Add unit test coverage for modules multisignatures #1723)
• node: most test are pending (Add full unit test coverage for partially covered node module #2446)
  - [ ] peers: tests __private functions are pending
• signatures: all test are pending (Add unit test coverage for signatures module #2445)
• transactions: some tests are pending

Which version(s) does this affect? (Environment, OS, etc...)

*.*.*

[MaciejBaj]

Peers module is currently being extracted to become a part of Lisk Elements, where all of the logic will be fully covered. It's not necessary to cover its private functions in Lisk Core. I am removing it from the list.