[humble] image_publisher: Fix loading of the camera info parameters on startup (backport #983)

[mergify]

As described in #965 camera info is not loaded from the file on node initialization, but only when the parameter is reloaded.

This PR resolves this issue and should be straightforward to port it to Humble, Iron and Jazzy.

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This is an automatic backport of pull request #983 done by Mergify.

[mergify]

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	both modified:   image_publisher/src/image_publisher.cpp

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[mikeferguson]

Fixed merge issue - waiting on CI