cabal: bump HUnit min version
cabal: bump HUnit min version

Ganeti is known to build on 1.6.

Signed-off-by: Apollon Oikonomopoulos <ed81ed0a45ccd5c8869bda52e38353a6299ee39e@debian.org>

mbakke/ganeti,mbakke/ganeti,ganeti/ganeti,ganeti/ganeti,ganeti/ganeti,mbakke/ganeti