Deployments are deemed different even if there are no changes in the Nexus CR

[LCaparelli]

Describe the bug
Deployments are deemed different even if there are no changes in the Nexus CR. This is due to the server setting default values we don't touch when creating the Deployment and the default comparator running reflect.DeepEqual() on the Deployment spec.

To Reproduce
Steps to reproduce the behavior:

1. Produce a CR which does not set the image Pull Policy
2. Observe the logs for the second reconciliation

Expected behavior
Required and deployed Deployments are deemed equal and it doesn't get updated.

Environment
Current version, any platform.

Additional context
We can bypass this altogether by having our own custom comparator that only cares about what we change. This way we don't have to worry about defaults the API server would set anyway and we won't perform as many comparisons using reflection, which will likely improve performance. On the other hand it's more code to maintain, but probably worth the trouble.