At the moment role does not increase volumes quota for the project
when BFV is enabled for Octavia. This might lead to Amphora
failures to spawn-up once default quota (of 10 volumes) is reached.
With that we also calculate amout of diskspace required based on the
instance limit.
It also changes flavor to contain 0 disk if BFV is enabled to ensure
that ephemeral is not gonna be used.
Change-Id: Ia35948cd2381b13d3792fc0029d93a9e176c884c
3b6f39ffbd