This is to fix an unintended side effect of file_format_check changes.
We were reading the trx system page (TRX_SYS_PAGE_NO) before starting
recovery and that resulted in redo logs not being applied to the page.
The fix is to force a reread by calling buf_pool_invalidate().
This, however, made necessary that any writes to page are deferred to
until after the redo log application.

Reviewed by: Sunny