fix: timezone set error

when system timezone change, User TimeZone property should not update
again if current set timezone is custom timezone

Log:

timedate1/handle_event.go

@@ -6,6 +6,7 @@ package timedate
 
 import (
 	"github.com/godbus/dbus/v5"
+	"github.com/linuxdeepin/go-lib/strv"
 )
 
 func (m *Manager) listenPropChanged() {
@@ -57,6 +58,12 @@ func (m *Manager) listenPropChanged() {
 			return
 		}
 		logger.Debug("property Timezone changed to", value)
+
+		// 如果要设置的时区是上海时区且当前的时区是自定义时区, 已经在SetTimezone更新过Timezone属性，此处不需要再更新
+		if value == "Asia/Shanghai" && strv.Strv(customTimeZoneList).Contains(m.Timezone) {
+			return
+		}
+
 		m.PropsMu.Lock()
 		m.setPropTimezone(value)
 		m.PropsMu.Unlock()