Skip `cabundle` secrets when Gitrepo does not include `GitRepo's .Spec.CABundle`

[mmartin24]

Description

On Rancher 2.9.-head we have introduced automatic cabundle secret creation when any gitrepo is deployed (perhaps after #2831?)

In this screenshot we can see how upon creation of 60 gitrepos without any certificate passed, it creates 60 cabundles secrets in 2.9.2 while 0 in 2.9.1:

Request

We should only create this cabundle secret when a certificate is passed

Steps to reproduce

• Deploy Rancher 2.9-head (> v2.9-3511f1655eaf53f86df3d87b9d4ff6f754d18d80-head)
• Create normal gitrepo without special certificate. For example this gitrepo containing a fleet.yaml defining a defaultNamespace and a deployment file with nginx image: https://github.com/rancher/fleet-test-data/tree/master/qa-test-apps/nginx-app
• Observe how cabundle is deployed.

The expected behavior would be

• not to deploy the cabundle secret in this case. @weyfonk , pointed out to perhaps skip secret creation if GitRepo's .Spec.CABundle field is empty
• be able to deploy it when an aditional certificate as this pem file is passed along when creating the gitrepo