For compatibility with legacy CLI if suffix-less number is passed,
it assumes amount in Mb.
Otherwise user is free to use suffixed number using suffixes b,k/K,M,G
Signed-off-by: Igor Mammedov <imammedo@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Andreas Färber <afaerber@suse.de> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>