ipareplica: Do no use IPA version to check for get_custodia_instance existance

The use of IPA versions to determine if get_custodia_instance should be
used was not optimal as the patch that introduced this has been back-ported
to the EL-7 package with verion 4.5.4. As get_custodia_instance was not
available before we can simply check if get_custodia_instance exists in
custodiainstance.