This commit updates the uct btl to change the transports parameter
into a priority list. The dc_mlx5, rc_mlx5, and ud transports to the
priority list. This will give better out of the box performance for
multi-threaded codes beacuse the *_mlx5 transports can avoid the mlx5
lock inside libmlx5_rdmav2.
This commit also fixes a number of leaks and a possible deadlock when
using RDMA.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
39be6ec15c