Always pass a callback as the last function parameter

[jondubois]

Expected behavior

If provided, the callback parameter to a function should be the last one.
Alternatively, if suitable, a Promise can be returned.

Actual behavior

Functions including blockchainReady, nodeStatus, getHeight, newRound, blocks, newBlock have a cb parameter, but it is not the last one in the function declaration (this violates the Node.js convention).

Steps to reproduce

See the test/common/utils/wait_for.js module.

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

1.2.0