engine: Change GetNetworksByStoragePoolIdQuery parameter

There is no need to use the StorageDomainAndPoolQueryParameters
as the parameters class of the query, since in this context only
the data-center id is relevant.

Change-Id: I7baad720ef06f625d26f764c0b3f81bb82ed5e40
Signed-off-by: Moti Asayag <masayag@redhat.com>