Potential crash with calling ibv_free_device_list before ibv_open_device

[Xiphoseer]

According to the man page for ibv_get_device_list.3, Client code should open all the devices it intends to use with ibv_open_device() before calling ibv_free_device_list(). This is not the case in BaseRDMA.cc, where the list is freed in line 95 before the device is opened in line 112. This doesn't crash immediately, because the ibv_device_t struct is copied in line 89 but it does decrement the internal reference count which unloads the device if it reaches zero and may cause some operations on the copy to crash if they are called.

[danfai]

This should be fixed by your code #13 which is now merged with #16 ?