Add "--wait" to asynchronous operation commands

Many actions in manila are asynchronous. The API service responds immediately to requests, but the fulfillment of the request can take a while. As a usability enhancement, we must introduce a "--wait" option to the CLI

Expected workflow:

1) Creating a share

$ manila create nfs 10 --name testshare --wait
<CLI waits on the share to become available before providing share details>

2) Deleting a share
$ manila delete testshare --wait
<CLI waits on the share to be deleted before returning to the prompt>

This user interaction can be extended to other commands such as:

a) Extending/Shrinking a share
b) Managing/unmanaging a share
c) Adding/Denying access rules to a share
d) Creating/Promoting/Deleting a share replica
e) Creating/Reverting/Deleting a snapshot
f) Managing/Unmanaging a snapshot
g) Allowing/Denying access to a snapshot
h) Managing/Unmanaging a share server
i) Deleting a share server
j) Force deleting a share/share-instance/snapshot/
k) Creating/Deleting a share group
l) Creating/Deleting a share group snapshot

Including into the newly introduced OSC interface.

Individual work items on this blueprint can be tracked and submitted as RFE "bugs" here on launchpad. If they are, the bug IDs will be added to the whiteboard.