[#3025] add ChangeLog entry

ChangeLog

@@ -1,3 +1,9 @@
+2207. [func] andrei
+ DHCP servers now initialize the database schema automatically on
+ startup or on reconfiguration if there is at least one database
+ backend configured and if the configured database is empty.
+ (Gitlab #3025)
+
 2206. [func] tmark
  Perfmon hook library now dumps the packet event stack
  of query packets to debug logging after they have been