in schizo/ompi, sets the new OMPI_MCA_mpi_oversubscribe environment
variable according to the node oversubscription state.
This MCA parameter is used to set the default value of the
mpi_yield_when_idle parameter.
This two steps tango is needed so the mpi_yield_when_idle setting
is always honored when set in a config file.
Refs. open-mpi/ompi#6433
Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>
(cherry-picked from cc97c0f6116ae62feef)
b004f4c391