Description of problem:
When creating child profiles for NTO, it is impossible to remove kernel command line parameters defined in parent profiles.

Version-Release number of selected component (if applicable):
All

How reproducible:
Always

Steps to Reproduce:
$ oc label node "worker-node" node-role.kubernetes.io/worker-rt=

$ oc create -f- <<EOF
apiVersion: tuned.openshift.io/v1
kind: Tuned
metadata:
  name: openshift-realtime
  namespace: openshift-cluster-node-tuning-operator
spec:
  profile:
  - data: |
      [main]
      summary=Custom OpenShift realtime profile
      include=openshift-node,realtime
      [variables]
      # isolated_cores take a list of ranges; e.g. isolated_cores=2,4-7
      isolated_cores=1
      [bootloader]
      cmdline_openshift_realtime=-intel_pstate=disable
    name: openshift-realtime

  recommend:
  - machineConfigLabels:
      machineconfiguration.openshift.io/role: "worker-rt"
    priority: 30
    profile: openshift-realtime
EOF

$ oc create -f- <<EOF
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfigPool
metadata:
  name: worker-rt
  labels:
    worker-rt: ""
spec:
  machineConfigSelector:
    matchExpressions:
      - {key: machineconfiguration.openshift.io/role, operator: In, values: [worker,worker-rt]}
  nodeSelector:
    matchLabels:
      node-role.kubernetes.io/worker-rt: ""
EOF

$ oc logs "NTO-operator-pod"
I0508 15:46:28.543553       1 main.go:24] Go Version: go1.13.4
I0508 15:46:28.543643       1 main.go:25] Go OS/Arch: linux/amd64
I0508 15:46:28.543653       1 main.go:26] node-tuning Version: v4.5.0-202005061719-0-g32eea34-dirty
I0508 15:46:28.546784       1 controller.go:780] trying to become a leader
I0508 15:46:28.570352       1 controller.go:785] became a leader
I0508 15:46:28.576367       1 controller.go:792] starting Tuned controller
I0508 15:46:28.676653       1 controller.go:850] started events processor/controller
I0508 15:47:39.803593       1 controller.go:406] updated Tuned rendered
I0508 15:47:39.817353       1 controller.go:517] updated profile ip-10-0-137-57.eu-west-1.compute.internal [openshift-realtime]
I0508 15:47:41.404917       1 controller.go:544] created MachineConfig 50-nto-worker-rt with kernelArguments: [skew_tick=1 isolcpus=1 intel_pstate=disable nosoftlockup tsc=nowatchdog]

Actual results:
intel_pstate=disable has not been removed.

Expected results:
intel_pstate=disable has been removed.

Additional info:
This is a tuned bug which was fixed upstream:
https://github.com/redhat-performance/tuned/pull/265