This manager class handles the work dealing with snapshots for a {@link HRegionServer}.
This provides the mechanism necessary to kick off a online snapshot specific {@link Subprocedure} that is responsible for the regions being served by this region server.If any failures occur with the subprocedure, the RegionSeverSnapshotManager's subprocedure handler, {@link ProcedureMember}, notifies the master's ProcedureCoordinator to abort all others.
On startup, requires {@link #start()} to be called.
On shutdown, requires {@link #stop(boolean)} to be called