sched/feasible: Validate CSIVolume's correctly

Previously we were looking up plugins based on the Alias Name for a CSI
Volume within the context of its task group.

Here we first look up a volume based on its identifier and then validate
the existence of the plugin based on its `PluginID`.

scheduler/feasible.go

@@ -230,20 +230,19 @@ func (c *CSIVolumeChecker) hasPlugins(n *structs.Node) bool {
 
 	ws := memdb.NewWatchSet()
 	for _, req := range c.volumes {
-		// Check that this node has a healthy running plugin with the right PluginID
-		plugin, ok := n.CSINodePlugins[req.Name]
-		if !(ok && plugin.Healthy) {
-			return false
-		}
-
 		// Get the volume to check that it's healthy (there's a healthy controller
 		// and the volume hasn't encountered an error or been marked for GC
 		vol, err := c.ctx.State().CSIVolumeByID(ws, req.Source)
-
 		if err != nil || vol == nil {
 			return false
 		}
 
+		// Check that this node has a healthy running plugin with the right PluginID
+		plugin, ok := n.CSINodePlugins[vol.PluginID]
+		if !(ok && plugin.Healthy) {
+			return false
+		}
+
 		if (req.ReadOnly && !vol.CanReadOnly()) ||
 			!vol.CanWrite() {
 			return false

scheduler/feasible_test.go

@@ -293,9 +293,9 @@ func TestCSIVolumeChecker(t *testing.T) {
 	noVolumes := map[string]*structs.VolumeRequest{}
 
 	volumes := map[string]*structs.VolumeRequest{
-		"foo": {
+		"baz": {
 			Type:   "csi",
-			Name:   "foo",
+			Name:   "baz",
 			Source: "volume-id",
 		},
 		"nonsense": {