Add a function computing optimal cluster score
Add a function computing optimal cluster score

With the addition of the total relative reserved memory, the optimal
cluster score no longer is 0 but the fraction of a machine that in
total is unused to keep N+1 redundancy. Add a function computing this
optimal value.

Signed-off-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>
Reviewed-by: Petr Pudlak <9d19625f8ee825a2c398462ed335cbcf98f79c32@google.com>

ganeti/ganeti,leshchevds/ganeti,leshchevds/ganeti,onponomarev/ganeti,dimara/ganeti,onponomarev/ganeti,ganeti/ganeti,grnet/snf-ganeti,yiannist/ganeti,ganeti/ganeti,mbakke/ganeti,bitemyapp/ganeti,andir/ganeti,mbakke/ganeti,mbakke/ganeti,yiannist/ganeti,bitemyapp/ganeti,andir/ganeti,leshchevds/ganeti,andir/ganeti,dimara/ganeti,yiannist/ganeti,grnet/snf-ganeti