[sonic-yang-models]: Add default values in leaf-lists of ports in son…

src/sonic-yang-models/yang-models/sonic-acl.yang

@@ -267,15 +267,23 @@ module sonic-acl {
 				}
 
 				leaf-list ports {
-                    /* union of leafref is allowed in YANG 1.1 */
+					/* union of leafref is allowed in YANG 1.1 */
 					type union {
 						type leafref {
 							path /port:sonic-port/port:PORT/port:PORT_LIST/port:port_name;
 						}
 						type leafref {
 							path /lag:sonic-portchannel/lag:PORTCHANNEL/lag:PORTCHANNEL_LIST/lag:portchannel_name;
 						}
+						type string {
+							pattern "";
+						}
 					}
+					/* Today in SONiC, we do not delete the list once
+					 * created, instead we set to empty list. Due to that
+					 * below default values are needed.
+					 */
+					default "";
 				}
 			}
 			/* end of ACL_TABLE_LIST */

src/sonic-yang-models/yang-models/sonic-portchannel.yang

@@ -60,9 +60,19 @@ module sonic-portchannel {
 
 				leaf-list members {
 					/* leaf-list members are unique by default */
-					type leafref {
-						path /port:sonic-port/port:PORT/port:PORT_LIST/port:port_name;
+					type union {
+						type leafref {
+							path /port:sonic-port/port:PORT/port:PORT_LIST/port:port_name;
+						}
+						type string {
+							pattern "";
+						}
 					}
+					/* Today in SONiC, we do not delete the list once
+					 * created, instead we set to empty list. Due to that
+					 * below default values are needed.
+					 */
+					default "";
 				}
 
 				leaf min_links {

src/sonic-yang-models/yang-models/sonic-vlan.yang

@@ -161,14 +161,6 @@ module sonic-vlan {
 				leaf admin_status {
 					type head:admin_status;
 				}
-
-				leaf-list members {
-					/* leaf-list members are unique by default */
-
-					type leafref {
-						path "/port:sonic-port/port:PORT/port:PORT_LIST/port:port_name";
-					}
-				}
 			}
 			/* end of VLAN_LIST */
 		}