cephfs: skip expand for BackingSnapshot volume

We should not call ExpandVolume for the BackingSnapshot
subvolume as there wont be any real subvolume created for
it and even if we call it the ExpandVolume will fail
fail as there is no real subvolume exists.

This commits fixes by adjusting the `if` check to ensure
that ExpandVolume will only be called either the
VolumeRequest is to create from a snapshot or volume
and BackingSnapshot is not true.

sample code here https://go.dev/play/p/PI2tNii5tTg

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

internal/cephfs/controllerserver.go

@@ -315,7 +315,7 @@ func (cs *ControllerServer) CreateVolume(
 	if vID != nil {
 		volClient := core.NewSubVolume(volOptions.GetConnection(), &volOptions.SubVolume,
 			volOptions.ClusterID, cs.ClusterName, cs.SetMetadata)
-		if sID != nil || pvID != nil && !volOptions.BackingSnapshot {
+		if (sID != nil || pvID != nil) && !volOptions.BackingSnapshot {
 			err = volClient.ExpandVolume(ctx, volOptions.Size)
 			if err != nil {
 				purgeErr := volClient.PurgeVolume(ctx, false)