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##### SUMMARY
<!--- Explain the problem briefly below -->
Fix iosxr interfaces zuul failure, which is failing coz of lowercase `loopback` instead of `Loopback` in iosxr. (ref: https://logs.zuul.ansible.com/03/61303/28b181fe1fcb3831516b336923ce39e29942ee50/third-party-check/ansible-test-network-integration-iosxr-python27/80fc31b/controller/ara-report/reports/01641385-035c-4e22-a0bd-fdfbf67a8cb9.html)
##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
iosxr_interfaces
##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
devel
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
zuul

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

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##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
iosxr_interfaces should pass as expected

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->
iosxr_interfaces fails
<!--- Paste verbatim command output between quotes -->
```paste below

```

"""
        Render config as dictionary structure and delete keys from spec for null values
        :param spec: The facts tree, generated from the argspec
        :param conf: The configuration
        :rtype: dictionary
        :returns: The generated config
        """
        config = deepcopy(spec)
        match = re.search(r'^(\S+)', conf)
        if match.group(1).lower() == "preconfigure":
            match = re.search(r'^(\S+ \S+)', conf)
        intf = match.group(1)
        if get_interface_type(intf) == 'unknown':
            return {}
        
        config['name'] = normalize_interface(intf)
        config['description'] = utils.parse_conf_arg(conf, 'description')
        if utils.parse_conf_arg(conf, 'speed'):
            config['speed'] = int(utils.parse_conf_arg(conf, 'speed'))
        if utils.parse_conf_arg(conf, 'mtu'):
            config['mtu'] = int(utils.parse_conf_arg(conf, 'mtu'))
        config['duplex'] = utils.parse_conf_arg(conf, 'duplex')
        enabled = utils.parse_conf_cmd_arg(conf, 'shutdown', False)
        config['enabled'] = enabled if enabled is not None else True
        return utils.remove_empties(config)