LeftHand: Implement v2 replication (managed)

LeftHand: Implement v2 replication (managed)

This patch implements the managed side of v2 replication in the HPE
LeftHand driver.

At this time, only periodic mode is supported with LeftHand arrays.

extra_spec value 'replication:sync_period' will specify the sync period
for the volume type. If it is not provided, it will be defaulted to 1800
seconds, or 30 minutes. 'replication:retention_count' determines how
many snapshots will be kept on the primary system. The maximum is 50,
and if the value is not specified, it defaults to 5.
'replication:remote_retention_count' determines how many snapshots will
be kept on the secondary system. The maximum is 50, and if the value is
not specified, it defaults to 5.

cinder.conf should have the replication config group (lefthandrep)
and at least one other target group (lefthand) as such:

[lefthand]
hpelefthand_api_url = https://10.10.10.10:8081/lhos
hpelefthand_username = user
hpelefthand_password = pass
hpelefthand_clustername = mgm-cluster-name-1
volume_backend_name = lefthand
volume_driver = cinder.volume.drivers.hpe.hpe_lefthand_iscsi.\
                HPELeftHandISCSIDriver

[lefthandrep]
hpelefthand_api_url = https://11.11.11.11:8081/lhos
hpelefthand_username = user
hpelefthand_password = pass
hpelefthand_clustername = mgm-cluster-name-2
volume_backend_name = lefthandrep
volume_driver = cinder.volume.drivers.hpe.hpe_lefthand_iscsi.\
                HPELeftHandISCSIDriver
replication_device = managed_backend_name:alex-devstack@lefthand#lefthand,
                     target_device_id:lh-id,
                     hpelefthand_api_url:https://10.10.10.10:8081/lhos,
                     hpelefthand_username:user,
                     hpelefthand_password:pass,
                     hpelefthand_clustername:mgm-cluster-name-1

Change-Id: I97959e78b71042642a9f36fc2cd8a4ad3c73f135
Implements: blueprint hp-lefthand-v2-replication
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