Added support of pool metadata replication for Disaster Recovery (TESTS ARE REQUIRED)
Added support of pool metadata replication for Disaster Recovery (TESTS ARE REQUIRED)

SR can be used now to store pool metadata for Disaster Recovery purpose.
RBD mirroring must be configured to replicate metadata and VMs' VDIs
between the two sites. RBD mirroring requires the Ceph Jewel release.

rposudnevskiy/RBDSR,suzj801/RBDSR,suzj801/RBDSR,rposudnevskiy/RBDSR