osc/rdma: performance improvments and bug fixes

[hjelmn]

This commit is a large update to the osc/rdma component. Included in
this commit:

• Add support for using hardware atomics for fetch-and-op and single
  count accumulate when using the accumulate lock. This will improve
  the performance of these operations even when not setting the
  single intrinsic info key.

• Rework how large accumulates are done. They now block on the get
  operation to fix some bugs discovered by an IBM one-sided test. I
  may roll back some of the changes if the underlying bug in the
  original design is discovered. There appear to be no real
  difference (on the hardware this was tested with) in performance so
  its probably a non-issue. References osc rdma hang with multiple windows #2530.

• Add support for an additional lock-all algorithm: on-demand. The
  on-demand algorithm will attempt to acquire the peer lock when
  starting an RMA operation. The lock algorithm default has not
  changed. The algorithm can be selected by setting the
  osc_rdma_locking_mode MCA variable. The valid values are two_level
  and on_demand.

• Make use of the btl_flush function if available. This can improve
  performance with some btls.

• When using btl_flush do not keep track of the number of put
  operations. This reduces the number of atomic operations in the
  critical path.

• Make the window buffers more friendly to multi-threaded
  applications. This was done by dropping support for multiple
  buffers per MPI window. I intend to re-add that support once the
  underlying performance bug under the old buffering scheme is
  fixed.

• Fix a bug in request completion in the accumulate, get, and put
  paths. This also helps with osc rdma hang with multiple windows #2530.

• General code cleanup and fixes.

Signed-off-by: Nathan Hjelm hjelmn@lanl.gov

[hjelmn]

opps, need to fix one small issue with the merge.