Replace underscores with hyphens in dns_domain

When creating Neutron networks, the name we use must be able to form a
valid DNS name. For this reason, we should replace underscores with
hyphens when we set the dns_domain property of any Neutron networks.

This change uses Jinja2 to format the string during template rendering.

Signed-off-by: Brendan Shephard <bshephar@redhat.com>
Change-Id: Ifc2e19d0499c12d2abd6ee7b25833451b9dab53e
Resolves: rhbz#2247835

network/network.j2

@@ -172,7 +172,7 @@ resources:
       dns_domain:
         list_join:
           - '.'
-          - - {{network.name.lower()}}
+          - - {{network.name.lower() | replace("_", "-")}}
             - {get_param: CloudDomain}
             - ''
       shared: {get_param: {{network.name}}NetShared}
@@ -301,7 +301,7 @@ outputs:
           dns_domain:
             list_join:
             - '.'
-            - - {{network.name.lower()}}
+            - - {{network.name.lower() | replace("_", "-")}}
               - {get_param: CloudDomain}
               - ''
           mtu: {{network.mtu|default('1500')}}