RDMA/cma: Allow enabling reuseaddr in any state

The rdma_cm only allows setting reuseaddr if the corresponding
rdma_cm_id is in the idle state.  Allow setting this value in other
states.  This brings the behavior more inline with sockets.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>