Improve port binding and db error msgs

[aionick]

Description

Please include a brief summary of the change that this pull request proposes. Include any relevant motivation and context. List any dependencies required for this change.

• Improve the p2p error message when unable to bind to a port. Also improved the db error messages for the case when two instances try using the same db and it locks out the second one.

This PR is dependent on the changes in Pr #507, the only commit that belongs to this PR is: 5f4ecec.

Fixes Issue #69.

Type of change

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• Bug fix.
• New feature.
• Breaking change (a fix or feature that causes existing functionality to not work as expected).
• Requires documentation update.

Testing

Please describe the tests you used to validate this pull request. Provide any relevant details for test configurations as well as any instructions to reproduce these results.

• Used manual testing, running two kernels on the same port and then running two kernels on the same db instance for each db we support.

Verification

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• I have self-reviewed my own code and conformed to the style guidelines of this project.
• New and existing tests pass locally with my changes.
• I have added tests for my fix or feature.
• I have made appropriate changes to the corresponding documentation.
• My code generates no new warnings.
• Any dependent changes have been made.