IBC-8: Fix missing checks on revision_number

[bluele]

No description provided.

[siburu]

@bluele In many files under the contracts/clients directory, revision_number is initialized to or compared to hardcoded 0s.
Shouldn't these 0s be replaced with DEFAULT_REVISION_NUMBER?

[bluele]

Thanks. I think your point is valid for LocalhostClient. In practice, revision_number is always expected to be 0, so probably there is no issue. However, it might still be worth refactoring. To enable this, I’ve added getRevisionNumber() function to the IIBCQuerier.
Since the clients/ directory is outside the scope of the current audit, I’ll consider making this change in the future.