Remove excess records from /etc/hosts

Before adding new records to /etc/hosts, remove all hostnames
that are managed by the model but have different addresses
than provided in the model.

Change-Id: Idf5a30429497c33027e6ba973e684ba0443a1edf

linux/network/host.sls

@@ -15,10 +15,31 @@ linux_hosts:
 
 {%- if host.names is defined %}
 
+{%- set clearers = [] %}
+{%- for etc_addr, etc_names in salt.hosts.list_hosts().iteritems() %}
+{%- set names_to_clear = [] %}
+{%- for host_name in host.names %}
+{%- if (host.address != etc_addr) and host_name in etc_names %}
+{%- do names_to_clear.append(host_name) %}
+{%- endif %}
+{%- endfor %}
+{%- if names_to_clear != [] %}
+{%- set clearer = "linux_host_" + name + "_" +  etc_addr + "_clear" %}
+{%- do clearers.append(clearer) %}
+
+{{ clearer }}:
+  host.absent:
+  - ip: {{ etc_addr }}
+  - names: {{ names_to_clear }}
+
+{%- endif %}
+{%- endfor %}
+
 linux_host_{{ name }}:
   host.present:
   - ip: {{ host.address }}
   - names: {{ host.names }}
+  - require: {{ clearers }}
 
 {%- if host.address in grains.ipv4 and host.names|length > 1 %}