Description of problem:

Let's assume we have the inventory:

[mons]
ceph-mon0 monitor_address=192.168.1.10
ceph-mon1 monitor_interface=eth1
ceph-mon2 monitor_address_block=192.168.1.0/24


the ceph.conf generation task will end up with:


fatal: [ceph-mon0]: FAILED! => {}

MSG:

'ansible.vars.hostvars.HostVarsVars object' has no attribute u'ansible_interface'



the reason is that it will assume monitor_address_block isn't defined even on
ceph-mon2 because looking for monitor_address_block instead of
hostvars[host]['monitor_address_block'], therefore it enters in the condition as default value:


    {%- else -%}
      {% set interface = 'ansible_' + (monitor_interface | replace('-', '_')) %}
      {% if ip_version == 'ipv4' -%}
        {{ hostvars[host][interface][ip_version]['address'] }}
      {%- elif ip_version == 'ipv6' -%}
        [{{ hostvars[host][interface][ip_version][0]['address'] }}]
      {%- endif %}
    {%- endif %}


monitor_interface is set with default value 'interface' so the interface
variable is built with 'ansible_' + 'interface'. It makes ansible throwing a
confusing message about 'ansible_interface'.


Steps to Reproduce:
1. Mix multiple monitor_address / monitor_address_block / monitor_interface on different mons in your inventory
2. Launch the deployment

Actual results:

ceph.conf generation task fails


Expected results:

ceph.conf is properly generated on all nodes.