Ignore deps already defined in a BOM

[ia3andy]

If a dependency is already defined in another BOM, it should be ignored when generating the locker bom.

Currently this means that if a dependency is defined in a BOM with exclusions, and this dependency is also locked using the locker, those exclusions will be ignored by Maven.

This is a edge case where you have a mvnpm bom with exclusions on top of the locker bom.