Make Checkpoint::checkpointId immutable

Change-Id: Idd56913f62979960bf01e955d2ac0770edc1bd29
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/172724
Reviewed-by: Paolo Cocchi <[email protected]>
Tested-by: Richard de Mellow <[email protected]>

Author: rdemellow

engines/ep/src/checkpoint.h

@@ -294,14 +294,6 @@ class Checkpoint {
         return checkpointId;
     }
 
-    /**
-     * Set the checkpoint Id
-     * @param id the checkpoint Id to be set.
-     */
-    void setId(uint64_t id) {
-        checkpointId = id;
-    }
-
     /**
      * Return the creation timestamp of this checkpoint in sec.
      */
@@ -643,7 +635,7 @@ class Checkpoint {
     CheckpointManager* manager = nullptr;
 
     EPStats& stats;
-    uint64_t                       checkpointId;
+    const uint64_t checkpointId;
     uint64_t                       snapStartSeqno;
     uint64_t                       snapEndSeqno;