Placate warnings on ganeti.outils_unittest.py
Placate warnings on ganeti.outils_unittest.py

Change ovf.py from using 'if foo:' to 'if foo is not None:' checks as
suggested by the FutureWarnings the OVF library raises otherwise.
This fixes issue 557.

Signed-off-by: Santi Raffa <6a214b96de92f36f05379f829a80c82d50682e4c@google.com>
Reviewed-by: Jose Lopes <0fb9c4f8511df4ec2ae28af879e9d462f6218a2c@google.com>

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