Merge PR #26895 into master

* refs/pull/26895/head:
	mds: convert unnecessary list usage to vector
	mds: convert get_*dirfrags to use vector
	mds: convert iterator loop to generic loop
	mds: list to std::list
	mds: constantize dump_loads

Reviewed-by: Jos Collin <jcollin@redhat.com>
Reviewed-by: Zheng Yan <zyan@redhat.com>