more realistic disk size for Ceph primary storage

### The required feature described as a wish

On Cloudstack 4.22.1.0 I created a RBD primary storage on a RADOS pool named "cloudstack-ssd".
Ceph reports that the pool used percentage is 5.17 and the maximum available capacity is 2.6 TiB.
```
# ceph df
--- RAW STORAGE ---
CLASS SIZE AVAIL USED RAW USED %RAW USED
hdd 33 TiB 31 TiB 1.3 TiB 1.3 TiB 3.89
ssd 8.7 TiB 8.3 TiB 447 GiB 447 GiB 5.00
TOTAL 41 TiB 40 TiB 1.7 TiB 1.7 TiB 4.12

--- POOLS ---
POOL ID PGS STORED OBJECTS USED %USED MAX AVAIL
cloudstack-ssd 4 32 169 GiB 48.15k 438 GiB 5.17 2.6 TiB
cloudstack-hdd 5 32 427 GiB 111.94k 1.2 TiB 3.96 9.7 TiB
```

But Cloudstack reports that "cloudstack-ssd" primary storage size is 42476.68 GB (about 41 TiB), which is Ceph total raw capacity.

I think that the value reported by Cloudstack is misleading.
It's not possible to compute the exact pool size because the raw space is contended between different pools.
But a better option could be that for a RBD storage Cloudstack displays the pool maximum available size and the used percentage (2.6 TiB and 5.17% in my configuration) instead of the total raw Ceph size (41 TiB in my configuration).

Comece localizando como o CloudStack reporta a capacidade do armazenamento primário RBD e como obtém os valores do pool Ceph. Compare a capacidade bruta total atual com os valores MAX AVAIL e USED do pool descritos aqui; o trabalho estará concluído quando a exibição do armazenamento primário refletir a capacidade e o uso específicos do pool sem representar incorretamente a capacidade bruta compartilhada.

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