Make getFQDN prefer cluster protocol family

In getFQDN, if the primary IP family of the cluster is known,
provide it as a hint.
Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Helga Velroyen <helgav@google.com>

src/Ganeti/Daemon.hs

@@ -334,7 +334,12 @@ getFQDNwithHints hints = do
 
 -- | Return the full qualified host name, honoring the vcluster setup.
 getFQDN :: IO String
-getFQDN = getFQDNwithHints Nothing
+getFQDN = do
+  familyresult <- Ssconf.getPrimaryIPFamily Nothing
+  getFQDNwithHints
+    $ genericResult (const Nothing)
+        (\family -> Just $ Socket.defaultHints { Socket.addrFamily = family })
+        familyresult
 
 -- | Returns if the current node is the master node.
 isMaster :: IO Bool