When attaching a group to the container, handle the group's
reserved regions and particularly the IOMMU_RESV_MSI region
which requires an IOVA allocator to be initialized through
the iommu_get_msi_cookie API. This will allow the MSI IOVAs
to be transparently allocated on MSI controller's compose().

Signed-off-by: Eric Auger <eric.auger@redhat.com>