Revert "md-raid: destroy the bitmap after destroying the thread"

commit 1d258758 upstream.

This reverts commit e151db8e. Because it
obviously breaks clustered raid as noticed by Neil though it fixed KASAN
issue for dm-raid, let's revert it and fix KASAN issue in next commit.

[1]. https://lore.kernel.org/linux-raid/a6657e08-b6a7-358b-2d2a-0ac37d49d23a@linux.dev/T/#m95ac225cab7409f66c295772483d091084a6d470

Fixes: e151db8e

 ("md-raid: destroy the bitmap after destroying the thread")
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>