Merge PR #29817 into master

* refs/pull/29817/head:
	doc: document that the kcephfs mount helper will search keyring files for secrets
	mount.ceph: fork a child to get info from local configuration
	mount.ceph: track mon string and path inside ceph_mount_info
	mount.ceph: add name and secret to ceph_mount_info
	mount.ceph: add ceph_mount_info structure
	mount.ceph: clean up debugging output and error messages
	mount.ceph: clean up return codes
	mount.ceph: add comment explaining why we need to modprobe
	mount.ceph: use bools for flags
	common: have read_secret_from_file return negative error codes

Reviewed-by: Kefu Chai <kchai@redhat.com>
Reviewed-by: Patrick Donnelly <pdonnell@redhat.com>