upgrade: better checking maintenance mode at engine level
upgrade: better checking maintenance mode at engine level

The auto-import of the hosted-engine storage domain from the
engine will change its SP so simply checking the list of
connected storage pool is safer.
vsdcli.list() returns a list of dictionaries, fixing it
to avoid 'unhashable type: 'dict''.

Bug-Url: https://bugzilla.redhat.com/1295427
Change-Id: I0d0389594c96c54653640b72d9acf4faf71e802a
Signed-off-by: Simone Tiraboschi <cb03129c66ba4da7ba7044049d0f43907bf857bb@redhat.com>
oVirt/ovirt-hosted-engine-ha,oVirt/ovirt-hosted-engine-ha,oVirt/ovirt-hosted-engine-ha,oVirt/ovirt-hosted-engine-ha