LKE-3931: Set maxVolumesPerNode to 7

This is a quick fix for the default case when we have 8 slots and one
slot is already taken by boot disk. There may be more slots in use by
non-PVC volumes such as swap but they are not the default in LKE.

Let's not let perfection be the enemy of good.

pkg/linode-bs/nodeserver.go

@@ -36,7 +36,7 @@ import (
 )
 
 const (
-	maxVolumesPerNode = 8
+	maxVolumesPerNode = 7
 )
 
 type LinodeNodeServer struct {