Bug fix: recurrent connection should have num_message_bits set to 0

[tnowotny]

This is true even if the layer is receiving input from a cyclic buffer (and hence input connections have a different setting)

Issue Number: #372

Objective of pull request:
In NetX converter, fix incorrect setting of num_message_bits in recurrent connections in the first hidden layer

Pull request checklist

Your PR fulfills the following requirements:

• Issue created that explains the change and why it's needed
• Tests are part of the PR (for bug fixes / features)
• [n/a] Docs reviewed and added / updated if needed (for bug fixes / features)
• PR conforms to Coding Conventions
• PR applys BSD 3-clause or LGPL2.1+ Licenses to all code files
• Lint (flakeheaven lint src/lava tests/) and (bandit -r src/lava/.) pass locally
• Build tests (pytest) passes locally

Pull request type

Please check your PR type:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation changes
• Other (please describe):

What is the current behavior?

• networks imported by the lava-dl NetX converter do not run correctly with cyclic buffer input if the first hidden layer is recurrent.

What is the new behavior?

• the networks do run correctly.

Does this introduce a breaking change?

• Yes
• No

Supplemental information

@timcheck knows all about this.