Every mapper is required to set the locale, which is why it is an error
if the locale attribute isn't found. Likewise, it is an error for any
mapper to set a NULL locale as it makes no sense. However, I can see
that maybe some compiler or static code checker might want to see
concrete evidence we checked it - so check it in the right place.
Backport the equivalent code from PRRTE as we know that works - more
confidence than trying to add another patch to this old code.
Signed-off-by: Ralph Castain <rhc@pmix.org>
79c426885a