Fix Potential Handler Leaks in the c/kubernetes/config/

[903d09f6-e821-4655-9e8b-7e6068b26f74]

This fix is for issue #243

1. Add pclose to config/exec_provider.c before kube_exec_and_get_result is returned by the exception handling.
2. Add fclose to config/kube_config_yaml.c before kubeyaml_save_kubeconfig is returned by the exception handling.

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[ityuhui]

To avoid duplication, I recommend moving all 3 blocks below

#ifndef _WIN32
            pclose(fp);
#else
            _pclose(fp);
#endif

to the last of function:

  end:
    if (result_string) {
        free(result_string);
        result_string = NULL;    // <-- This time I added a new line
    }

    if (fp) {
#ifndef _WIN32
        pclose(fp);
#else
        _pclose(fp);
#endif
        fp = NULL;   // <-- This time I added a new line
    }

    return rc;

And change https://github.com/kubernetes-client/c/blob/02a71845ae56ebb9910fd578f814fae9a68b435a/kubernetes/config/exec_provider.c#L83

to

rc = -1;
goto end;

[903d09f6-e821-4655-9e8b-7e6068b26f74]

I agree to your suggestion. HERE is the revision. Thank you.

[ityuhui]

I'm OK with this PR. Please wait a moment to see if @brendandburns has a comment.

[brendandburns]

/lgtm /approve

thanks for the PR!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 903d09f6-e821-4655-9e8b-7e6068b26f74, brendandburns

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