Huawei driver check before associating LUN to a LUN group

Huawei driver check before associating LUN to a LUN group

This commit fixes the following problems:
* Change in huawei_t.py removes the duplicated wwns
  returned from the array.
* Change in rest_common.py adds log print for response
  data from the array.
* Change in rest_common.py does a check before associating
  a LUN to a LUN group.
* Change in rest_common.py fixes the REST request.
* Change in ssh_common.py checks whether the hostlunid
  have already been assigned.

Closes-Bug: #1411904
Change-Id: I862ed5d71780fb7b8cbc5ed257072ea1113fead7