Depend Arbitrary (Map k a) instance on QuickCheck version
Depend Arbitrary (Map k a) instance on QuickCheck version

QuickCheck version 2.8.2 newly introduced an Arbitrary instance
for Maps. As this instance was not present in earlier versions
of QuickCheck, we have it in our TestCommon module as well. Make
this definition depended on an older version of QuickCheck being
used, to avoid duplicate (albeit equivalent) instance declarations.

Signed-off-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>
Reviewed-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>

ganeti/ganeti,ganeti/ganeti,andir/ganeti,mbakke/ganeti,leshchevds/ganeti,mbakke/ganeti,mbakke/ganeti,onponomarev/ganeti,leshchevds/ganeti,andir/ganeti,andir/ganeti,leshchevds/ganeti,onponomarev/ganeti,ganeti/ganeti