Merge PR #38820 into master

* refs/pull/38820/head:
	include: use narrower ostream instead of iostream
	mds: remove unused fstream header
	mds: use narrower ostream header instead of sstream
	mds: remove unused iostream header
	mds: remove unused unix headers

Reviewed-by: Jos Collin <jcollin@redhat.com>
Reviewed-by: Rishabh Dave <ridave@redhat.com>

diff --cc src/mds/cephfs_features.cc
Simple merge