Filter out link-local ipv6 address in loadbalancer

On puppet 3, which uses facter 2, the $::ipaddress6 fact explicitly
filters out all link-local address[1]. On puppet 4, which uses facter 3,
the $::ipaddress6 fact only removes the link-local address if can find a
better one[2]. The beaker tests reveal that haproxy won't bind to the
ipv6 local address and will fail to start, with errors like:

  Starting proxy balance_git_daemon: cannot bind socket [fe80::5054:ff:fec5:7095:9418]

This matters in CI test cases where the test nodes don't have real ipv6
addresses.

This patch restores the puppet 3 behavior of ignoring the ipv6 address if
it's a link-local address.

[1] https://github.com/puppetlabs/facter/blob/2.x/lib/facter/ipaddress6.rb#L31
[2] https://docs.puppet.com/facter/3.1/release_notes.html#regression-fix-avoid-reporting-link-local-ipv6-addresses-if-a-valid-address-is-available

Change-Id: I481403a3a988211effd22c8524171379aea9ccf9

manifests/lb.pp

@@ -81,8 +81,18 @@ class cgit::lb (
     defaults_options => $defaults_options,
   }
 
+  # NOTE(cmurphy) If the only available ipv6 address is a link-local address,
+  # facter won't filter it out:
+  # https://docs.puppet.com/facter/3.1/release_notes.html#regression-fix-avoid-reporting-link-local-ipv6-addresses-if-a-valid-address-is-available
+  # But we don't want haproxy to try to bind to a link local address, so filter
+  # it out
+  if $::ipaddress6 =~ /^fe[89a-f]/ {
+    $_ipaddress6 = undef
+  } else {
+    $_ipaddress6 = $::ipaddress6
+  }
   # The three listen defines here are what the world will hit.
-  $haproxy_addresses = delete_undef_values([$::ipaddress, $::ipaddress6])
+  $haproxy_addresses = delete_undef_values([$::ipaddress, $_ipaddress6])
 
   haproxy::listen { 'balance_git_http':
     ipaddress        => $haproxy_addresses,