fix:DruidDatasource无法关闭closed (baomidou#637)

[shen3]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style
• Refactor
• Doc
• Other, please describe:

The description of the PR:
1、closeDataSource方法进来默认直接把数据源dataSource 赋值给 realDatasource。下面if...else条件如果为真，realDatasource会被重新赋值，不影响原来的逻辑。
2、如果dataSource 是Druid等其他的数据源，也能够被closed。

[huayanYu]

不喜欢提前赋值的这种方式

[shen3]

DataSource realDataSource = null;
if (dataSource instanceof ItemDataSource) {
realDataSource = ((ItemDataSource) dataSource).getRealDataSource();
} else {
if (seata) {
if (dataSource instanceof DataSourceProxy) {
DataSourceProxy dataSourceProxy = (DataSourceProxy) dataSource;
realDataSource = dataSourceProxy.getTargetDataSource();
}
}
if (p6spy) {
if (dataSource instanceof P6DataSource) {
Field realDataSourceField = P6DataSource.class.getDeclaredField("realDataSource");
realDataSourceField.setAccessible(true);
realDataSource = (DataSource) realDataSourceField.get(dataSource);
}
}
}

这种？

if (null == realDataSource) {
realDataSource = dataSource;
}

if (null != realDataSource) {
DataSourceDestroyer destroyer = new DefaultDataSourceDestroyer();
if (graceDestroy) {
destroyer.asyncDestroy(ds, realDataSource);
} else {
destroyer.destroy(ds, realDataSource);
}
}

[huayanYu]

en

[shen3]

已重新提交