Lightos connector - refactor disconnect volume
Lightos connector - refactor disconnect volume

Disconnect volume needs to perform the following operations:
1. Update our connection DB that the volume has been disconnected
2. Flush any pending I/Os on the device file
3. Update the discovery-client that the volume has been disconnected.

Signed-off-by: Yuval Brave  <4e937afa6b629a6bab3cefd3f1f5692c268d79a3@lightbitslabs.com>
Change-Id: I5cd5456c4cc3e415fd08b678cc57fc794dc0621b

openstack/os-brick,openstack/os-brick