Mention hail network incompatibility in manpages

We can't fix this in the 2.7 version, so it should be documented.
Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Thomas Thrainer <thomasth@google.com>

man/gnt-network.rst

@@ -19,6 +19,14 @@ administration in the Ganeti system. Each instance NIC can be connected
 to a network via the ``network`` NIC parameter. See **gnt-instance**\(8)
 for more details.
 
+BUGS
+----
+
+The ``hail`` iallocator hasn't been updated to take networks into
+account in Ganeti 2.7. The only way to guarantee that it works correctly
+is having your networks connected to all nodegroups. This will be fixed
+in a future version.
+
 COMMANDS
 --------
 

man/hail.rst

@@ -118,6 +118,14 @@ EXIT STATUS
 The exist status of the command will be zero, unless for some reason
 the algorithm fatally failed (e.g. wrong node or instance data).
 
+BUGS
+----
+
+Networks (as configured by **gnt-network**\(8)) are not taken into
+account in Ganeti 2.7. The only way to guarantee that they work
+correctly is having your networks connected to all nodegroups. This will
+be fixed in a future version.
+
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