Fix lint on qa_cluster.py
Fix lint on qa_cluster.py

pep8 wants two blank lines after TestUpgrade. The previous commit gave
it one. This commit gives it the second.

Signed-off-by: Santi Raffa <6a214b96de92f36f05379f829a80c82d50682e4c@google.com>
Reviewed-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>

ganeti/ganeti,dimara/ganeti,apyrgio/ganeti,leshchevds/ganeti,bitemyapp/ganeti,andir/ganeti,leshchevds/ganeti,yiannist/ganeti,ganeti/ganeti,mbakke/ganeti,yiannist/ganeti,grnet/snf-ganeti,apyrgio/ganeti,mbakke/ganeti,andir/ganeti,andir/ganeti,yiannist/ganeti,dimara/ganeti,grnet/snf-ganeti,ganeti-github-testing/ganeti-test-1,onponomarev/ganeti,bitemyapp/ganeti,leshchevds/ganeti,mbakke/ganeti,onponomarev/ganeti,ganeti-github-testing/ganeti-test-1,ganeti/ganeti