This commit fixes a bug where add_procs can incorrectly return an
error when going through the dynamic add_procs path. This doesn't
happen normally, only when pml/ob1 is not in use.
References #6201
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
(cherry picked from commit 30b8336cb40e586e5d926b2b52cd78bf3751e5d3)