RDMA/cxgb3: Fixes for "normal close" failures

Fixes for "normal close" failures:

- Start normal close timer when moving to CLOSING state.
- Handle ABORTING state in close_con_rpl().
- Stop timer correctly on abort during a normal close.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>