[MANUALLY BACKPORT v1.4.x ] fix: mount the whole host to engine im

[ChanYiLin]

ref: https://github.com/longhorn/longhorn/issues/7501 https://github.com/longhorn/longhorn/issues/7730

To allow engine instance manager to inspect mount point, we need to mount the whole host to the pod After v1.5.x, engine/replica instance manager become one, and it mount the whole host to the pod as well.