Use nsenter to write multipath.conf in host's mount namespace instead
of trying to write to /host/etc which is read-only in containers.
Talos mounts /etc as read-only in container namespaces but allows writes
in the host mount namespace. This fix uses nsenter to access PID 1's
mount namespace where /etc is writable.
Also removed unnecessary volumeMounts and volumes since we're using
nsenter instead of hostPath mounts.
Fixes: Init:Error - 'can't create /host/etc/multipath.conf: Read-only file system'
002d6799b1