Fix wrong size of /home shown by node-exporter (#87)

Node-exporter calculates wrong disk space if /home is a separate partition
since systemd protects /home from it.

Change protection to read-only if /home is a mountpoint.

[minor] release

templates/node_exporter.service.j2

@@ -29,7 +29,11 @@ SyslogIdentifier=node_exporter
 Restart=always
 
 PrivateTmp=yes
+{% for m in ansible_mounts if m.mount == '/home' %}
+ProtectHome=read-only
+{% else %}
 ProtectHome=yes
+{% endfor %}
 NoNewPrivileges=yes
 
 {% if node_exporter_systemd_version | int >= 232 %}