rootDisk on containers can have different device Id (#10259)

use `/etc/hosts` instead of `/` to check for common
device id, if the device is same for `/etc/hosts`
and the --bind mount to detect root disks.

Bonus enhance healthcheck logging by adding maintenance
tags, for all messages.

pkg/disk/root_disk_unix.go

@@ -31,7 +31,7 @@ func IsRootDisk(diskPath string) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	rootInfo, err := os.Stat("/")
+	rootInfo, err := os.Stat("/etc/hosts")
 	if err != nil {
 		return false, err
 	}