Haproxy: Allow a port number to be set for a server

This overrides the default port set in haproxy_applications. Useful in
migration scenarios

roles/haproxy/templates/haproxy_backend.cfg.j2

@@ -34,7 +34,7 @@
   cookie HTTPSERVERID insert nocache indirect httponly secure maxidle {{ haproxy_cookie_max_idle }}
 
   {% for server in application.servers %}
-  server {{ server.label }} {{ server.ip }}:{{ application.port }} cookie {{ server.label }} check inter 8000 fall 5 rise 2 maxconn {{ application.maxconn | default('35') }} {% if application.sslbackend is defined%} ssl verify required verifyhost {{ application.backend_vhost_name }} ca-file {{ application.backend_ca_file }}{% endif %} weight 100
+  server {{ server.label }} {{ server.ip }}:{% if server.port is defined %}{{ server.port }}{% else %}{{ application.port }}{% endif %} cookie {{ server.label }} check inter 8000 fall 5 rise 2 maxconn {{ application.maxconn | default('35') }} {% if application.sslbackend is defined%} ssl verify required verifyhost {{ application.backend_vhost_name }} ca-file {{ application.backend_ca_file }}{% endif %} weight 100
 
   {% endfor %}
 
@@ -60,7 +60,7 @@
   cookie HTTPSERVERIDSTAGING insert nocache indirect httponly secure maxidle {{ haproxy_cookie_max_idle }}
 
   {% for server in application.stagingservers %}
-  server {{ server.label }} {{ server.ip }}:{{ application.port }} cookie {{ server.label }} check inter 8000 fall 5 rise 2 maxconn {{ application.maxconn | default('35') }} {% if application.sslbackend is defined%} ssl verify required verifyhost {{ application.backend_vhost_name }} ca-file {{ application.backend_ca_file }}{% endif %} weight 100
+  server {{ server.label }} {{ server.ip }}:{% if server.port is defined %}{{ server.port }}{% else %}{{ application.port }}{% endif %} cookie {{ server.label }} check inter 8000 fall 5 rise 2 maxconn {{ application.maxconn | default('35') }} {% if application.sslbackend is defined%} ssl verify required verifyhost {{ application.backend_vhost_name }} ca-file {{ application.backend_ca_file }}{% endif %} weight 100
 
   {% endfor %}
 {% endif %}