public long assign(RegionInfo regionInfo, ServerName sn) throws IOException {
    TransitRegionStateProcedure proc = createAssignProcedure(regionInfo, sn, false, false);
    ProcedureSyncWait.submitAndWaitProcedure(master.getMasterProcedureExecutor(), proc);
    return proc.getProcId();
  }
Create an assign TransitRegionStateProcedure. Does NO checking of RegionState. Presumes
appriopriate state ripe for assign.
@see #createAssignProcedure(RegionInfo, ServerName, boolean, boolean)
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/AssignmentManager.java