rdma: bug fixes

1. Fix small memory leak in parsing inet address from command line in data_init()
2. Fix ibv_post_send() return value check and pass error code back up correctly.
3. Fix rdma_destroy_qp() segfault after failure to connect to destination.

Reported-by: frank.yangjie@gmail.com
Reported-by: dgilbert@redhat.com
Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
