Correct containers' `volume_mounts`'s type.

[lonegunmanb]

Describe your changes

According to the provider's schema, volume_mounts should be a list of object rather than an optional object. This pr correct the variable's type so we can define multiple volume mounts for a container template.

Issue number

000

Checklist before requesting a review

• [ ] The pr title can be used to describe what this pr did in CHANGELOG.md file
• [ ] I have executed pre-commit on my machine
• [ ] I have passed pr-check on my machine

Thanks for your cooperation!