The send inline optimization uses the btl_sendi function to achieve lower
latency and higher message rates. Before this commit BTLs were allowed to
assume the descriptor was non-NULL and were expected to return a valid
descriptor if the send could not be completed using btl_sendi. This
behavior was fine until the usage of btl_sendi was changed in ob1. This
commit allows the caller to specify NULL for the descriptor. The affected
btls have been updated to handle this case.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
fc7397949c