Made to lower invariant and fixed minor bugs after gRPC update

[ghost]

Purpose

Made sure all call which creates Hex string make them to lower invariants.

This since from gRPC v1 we have from the nodes returned hex strings in lower invariants. Hence if some have stored these references in some storage and selecting using case sensitive queries, then their logic will be broken.

Changelog not updated since all changes in this PR only affects code which hasn’t been released yet.

Changes

Make Hex strings consistent with earlier protocol.

Also fix minor bugs after gRPC update.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• [-] (If necessary) I have updated the CHANGELOG.

[bisgardo]

LGTM. Ideally all the changes should have been covered by unit tests.