gcp_container_cluster kubectl config malformed yaml

##### SUMMARY
When using the `gcp_container_cluster` module with the `kubectl_path` argument, the output yaml contains [PyYaml object tags](https://pyyaml.org/wiki/PyYAMLDocumentation#objects). The resulting yaml file is invalid when tags are present and cannot be properly read by `kubectl`

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
This bug is present in the `gcp_container_cluster` module.

##### ANSIBLE VERSION

```
ansible 2.9.6
config file = /etc/ansible/ansible.cfg
configured module search path = [u'/home/tatemz/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
ansible python module location = /usr/lib/python2.7/dist-packages/ansible
executable location = /usr/bin/ansible
python version = 2.7.17 (default, Nov 7 2019, 10:07:09) [GCC 9.2.1 20191008]
```

##### CONFIGURATION

```

```

##### OS / ENVIRONMENT

##### STEPS TO REPRODUCE

```yaml
- name: Create a GKE cluster
gcp_container_cluster:
name: my-gke-cluster
initial_node_count: 1
location: us-central1-a
project: myproject-id
auth_kind: serviceaccount
service_account_file: "/path/to/service/account.json"
state: present
kubectl_path: "/tmp/kubectl.config"
```

##### EXPECTED RESULTS

The output Kube config should have valid cluster server endpoints.

```yaml
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: CERRT_DATA
server: 'https://12.345.678.90'
name: my-gke-cluster
...
```

##### ACTUAL RESULTS

The invalid output Kube config may look like below (note the `clusters[0].cluster.server`).

```yaml
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: CERRT_DATA
server: !!python/unicode 'https://12.345.678.90'
name: my-gke-cluster
...
```

Start at the gcp_container_cluster module's kubectl_path handling and reproduce the issue with the playbook shown, inspecting the generated kubeconfig YAML. Done means the cluster server endpoint and other values are emitted as valid YAML without PyYAML object tags, so kubectl can read the file.

Written by the indexing model from the issue text.