Improve logs on SecondaryStorageManagerImpl and few refactors (#4955)

Co-authored-by: Daniel Augusto Veronezi Salvador <daniel@scclouds.com.br>

Author: GutoVeronezi

engine/schema/src/main/java/com/cloud/dc/DataCenterVO.java

@@ -471,4 +471,10 @@ public void setIp6Dns2(String ip6Dns2) {
     public PartitionType partitionType() {
         return PartitionType.Zone;
     }
+
+    @Override
+    public String toString() {
+        return String.format("Zone {\"id\": \"%s\", \"name\": \"%s\", \"uuid\": \"%s\"}", id, name, uuid);
+    }
+
 }

engine/schema/src/main/java/com/cloud/vm/VMInstanceVO.java

@@ -504,14 +504,9 @@ public void setRemoved(Date removed) {
         this.removed = removed;
     }
 
-    transient String toString;
-
     @Override
     public String toString() {
-        if (toString == null) {
-            toString = new StringBuilder("VM[").append(type.toString()).append("|").append(getInstanceName()).append("]").toString();
-        }
-        return toString;
+        return String.format("VM instance {\"id\": \"%s\", \"name\": \"%s\", \"uuid\": \"%s\", \"type\"=\"%s\"}", id, getInstanceName(), uuid, type);
     }
 
     @Override