[openib-general] [libibverbs/examples] pingpong tests cleanup (resource destroy + ack events + asprintf failure check)

[Roland Dreier]

Looks pretty good, but could you please:

 - split off the asprintf() checks into a separate patch ("one idea
   per patch").
 - change the code so it keeps a count of cq events and then just
   does one ibv_ack_cq_events(cq, num_cq_events) at the end.  If
   people are going to use this code as an example, then we should
   avoid expensive calls to ibv_ack_cq_events() (which has to do a
   pthread_mutex_lock()/unlock() and a pthread_cond_signal()) in the
   main data-moving flow.

thanks...