Fix for issue #163
Fix for issue #163

OpenShift: Stale VLUN entries are still present in host and 3par array after deleting ReplicaSets/Deployments.

The logs revealed that plugin receives four mount-volume requests. Expectation is that for each of these requests, there would be a unique mount-id. However, pair of two requests come in with same mount-id. Since plugin doesn't check for the uniqueness of mount-id (as we expected Docker engine would always send a unique value), plugin adds all of them to the mount-id list i.e. four entries in the list.

However, plugin receives only two un-mount requests and this leaves the mount-id-list with two entries. And hence actual un-mounting of the volume doesn't happen which leaves VLUN entries intact both on the host and the array.

Disallow duplicate mount-ids from getting added to mount-id-list.

hpe-storage/python-hpedockerplugin,hpe-storage/python-hpedockerplugin