Commit open-mpi/ompi@1a3597aam changed the type of the `convertor`
variable from `ompi_osc_base_convertor_t` (which contained an
`opal_convertor_t`) to an `opal_convertor_t`. Hence, using memchecker
to ensure that the inner convertor of the `ompi_osc_base_convertor_t`
is considered initialized is now unnecessary.