Fix Docker runtime check to happen only during install (#8667)

Closes #8583 

Even though #7468 removed the Docker container runtime check from `linkerd check --pre` to `linkerd install` runtime error, we still do a dry run of the installation so that we can render the control plane manifests. Therefore, we still hit this check which results in not being able to run `linkerd check --pre` when nodes are using the Docker container runtime. This fixes the issue by introducing a `dryRun` flag that we check beforehand.

```shell
❯ kubectl get nodes docker-desktop -o jsonpath='{.status.nodeInfo.containerRuntimeVersion}'
docker://20.10.16

❯ bin/linkerd check --pre
Linkerd core checks
===================
...
```

Signed-off-by: Kevin Leimkuhler <kleimkuhler@icloud.com>

cli/cmd/check.go

@@ -10,15 +10,13 @@ import (
 	"strings"
 	"time"
 
-	"github.com/linkerd/linkerd2/cli/flag"
 	charts "github.com/linkerd/linkerd2/pkg/charts/linkerd2"
 	pkgcmd "github.com/linkerd/linkerd2/pkg/cmd"
 	"github.com/linkerd/linkerd2/pkg/healthcheck"
 	"github.com/linkerd/linkerd2/pkg/k8s"
 	"github.com/linkerd/linkerd2/pkg/version"
 	"github.com/spf13/cobra"
 	"github.com/spf13/pflag"
-	valuespkg "helm.sh/helm/v3/pkg/cli/values"
 )
 
 type checkOptions struct {
@@ -268,20 +266,25 @@ func getExtensionCheckFlags(lf *pflag.FlagSet) []string {
 }
 
 func renderInstallManifest(ctx context.Context) (*charts.Values, string, error) {
+	// Create the default values.
+	k8sAPI, err := k8s.NewAPI(kubeconfigPath, kubeContext, impersonate, impersonateGroup, 30*time.Second)
+	if err != nil {
+		return nil, "", err
+	}
 	values, err := charts.NewValues()
 	if err != nil {
 		return nil, "", err
 	}
-
-	k8sAPI, err := k8s.NewAPI(kubeconfigPath, kubeContext, impersonate, impersonateGroup, 30*time.Second)
+	err = initializeIssuerCredentials(ctx, k8sAPI, values)
 	if err != nil {
-		return values, "", err
+		return nil, "", err
 	}
 
+	// Use empty valuesOverrides because there are no option values to merge.
 	var b strings.Builder
-	err = installControlPlane(ctx, k8sAPI, &b, values, []flag.Flag{}, valuespkg.Options{})
+	err = renderControlPlane(&b, values, map[string]interface{}{})
 	if err != nil {
-		return values, "", err
+		return nil, "", err
 	}
 	return values, b.String(), nil
 }