Improved error logging when trying to save a product

[woutersamaey]

Description

Improved error logging for 2 cases:

• The original exception was not passed as $cause in the new exception, when
• The original exception is not logged sometimes when trying to save a product
  Now we can easily know the underlying exception.

Fixed Issues (if relevant)

None. General improvement

Manual testing scenarios

None. General improvement

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-cicd2]

All committers have signed the CLA.