Can't force-create snapshot by an non-exist error volume

If we create an LVM volume whose size larger than
rest space in VG, the volume would not exist with
error status.
But then we still can force create a snapshot
by this volume, and the snapshot's status is available.
In the code,I found in create_lv_snapshot,
it return False when fail to get the volume.
However, raising an exception is only way to be
handle outside.
So, we should raise exception instead of return False.

Closes-Bug: #1283338

Change-Id: I80256f19d66da460c95ff23834abb79a557763bf
Adds xiv_chap to xiv/ds8k driver configuration

In order to support CHAP, xiv_chap was added to
the driver configuration. Valid values are disabled
and enabled (default: disabled)

Change-Id: I0c68f581ad78a87a506b00ab308806f4a8fa78a8
DocImpact
Closes-Bug: #1288816
Merge "Can't force-create snapshot by an non-exist error volume"
Merge "Adds xiv_chap to xiv/ds8k driver configuration"
Serialize the notification payload

Notification payload in oslomessaging needs to be
serialized correctly, currently it's not.

Use json to encode the payload.
Closes-Bug: 1294949

Change-Id: Idb2c13981cc1c60ed02445a28220d1dab1529d2b