Fix arbitrary ConfigData object generation

The Cluster object, as it is defined right now, has many '[String]'
members, which means that in a standard arbitrary generator these will
become very big, which is the reason for the current slowness of the
test 'Config_serialisation'.

By resizing the generator to 8 (arbitrary chosen to limit the list
length and the string sizes), and by reducing a bit the node count, we
can make this test be as fast as the others (about 10x
improvement). This means we can test more cases, for the same cost.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

htest/Test/Ganeti/Objects.hs

@@ -187,7 +187,7 @@ genEmptyCluster ncount = do
   grp <- arbitrary
   let contgroups = Container $ Map.singleton guuid grp
   serial <- arbitrary
-  cluster <- arbitrary
+  cluster <- resize 8 arbitrary
   let c = ConfigData version cluster contnodes contgroups continsts serial
   return c
 
@@ -227,7 +227,7 @@ prop_Inst_serialisation = testSerialisation
 -- | Check config serialisation.
 prop_Config_serialisation :: Property
 prop_Config_serialisation =
-  forAll (choose (0, maxNodes) >>= genEmptyCluster) testSerialisation
+  forAll (choose (0, maxNodes `div` 4) >>= genEmptyCluster) testSerialisation
 
 testSuite "Objects"
   [ 'prop_fillDict