Fix a bug in the ob1 optimizations that can cause a segfault.

btl sendi functions currently can not handle the descriptor being NULL. The
send inline optimization was assuming (incorrectly) that NULL was ok.

cmr=v1.7.5:ticket=#4149
btl/ugni: fix leak in new sendi function.

cmr=v1.7.5:ticket=#4151
coll/ml: cleanup some merge related errors

cmr=v1.7.5:ticket=#4158