Description of problem:

If MultipathdCustomConfigFile is present and the multipath.conf file has blacklist or blacklist_exceptions section, tripleo-ansible modifies the multipath.conf file incorrectly like the following example:

<Original multipath.conf file configured by MultipathdCustomConfigFile>
~~~
blacklist {
    devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
    devnode "^hd[a-z]"
}

blacklist_exceptions {
    device {
        product "XXXX"
        vendor "XXXX"
    }
}
~~~

<Deployed multipath.conf file on overcloud Compute node>
~~~
blacklist {
}                    <==================(*) added incorrectly
    devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
    devnode "^hd[a-z]"
}

blacklist {          <==================(*) Changed to blacklist from blacklist_exceptions
}                    <==================(*) added incorrectly
    device {
        product "XXXX"
        vendor "XXXX"
    }
}
~~~

The above change is made by the following Ansible tasks:

  - https://github.com/openstack/tripleo-ansible/blob/stable/train/tripleo_ansible/roles/tripleo_multipathd/tasks/configure.yml#L47-L91

I think these Ansible tasks shouldn't run when MultipathdCustomConfigFile is present.



Version-Release number of selected component (if applicable):
My customer observed this issue on their RHOSP 16.2.4 environment first.
Then I reproduced the same issue on my RHOSP 16.2.4 lab.


How reproducible:
Steps to Reproduce:
1. In undercloud, create /var/lib/mistral/multipath.conf file which includes blacklist section or blacklist_exceptions section.
2. Create the following environment file.
   ~~~
   parameter_defaults:
     MultipathdCustomConfigFile: /var/lib/mistral/multipath.conf
   ~~~
3. Deploy overcloud with the following environment files
   ~~~
   $ openstack overcloud deploy \
      :
     -e /usr/share/openstack-tripleo-heat-templates/environments/multipathd.yaml
     -e <env file created by step 2>
      :
   ~~~
4. Check /etc/multipath.conf on Compute nodes.

Doc : https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/16.2/html/storage_guide/assembly-configuring-the-block-storage-service_osp-storage-guide#proc-configuring-multipath-on-new-deployments_configuring-cinder


Actual results:
/etc/multipath.conf on Compute nodes retains valid contents.


Expected results:
/etc/multipath.conf is modified incorrectly.
"blacklist" section bracket is closed incorrectly.
"blacklist_exceptions" section is changed to "blacklist"