tools/pd-control: add option of disable-namespace-relocation

tools/pd-control.md

@@ -116,6 +116,7 @@ Usage:
   "disable-make-up-replica": "false",
   "disable-remove-extra-replica": "false",
   "disable-location-replacement": "false",
+  "disable-namespace-relocation": "false",
   "schedulers-v2": [
     {
       "type": "balance-region",
@@ -263,6 +264,8 @@ The configuration above is global. You can also tune the configuration by config
 
 - `disable-location-replacement` is used to disable the isolation level check. When you set it to `true`, PD does not improve the isolation level of Region replicas by scheduling.
 
+- `disable-namespace-relocation` is used to disable relocation region to stores of its namespace. When you set it to `true`, PD does not move regions to stores where they belongs to.
+
 ### `config delete namespace \<name\> [\<option\>]`
 
 Use this command to delete the configuration of namespace.