Fix error in chaining stages in ReactiveStatelessWithBatchTest

[DavideD]

Ooops... a bit embarassing.

Some methods call .thenApply instead of .thenCompose.

Here's an example

.thenApply( pigs -> {
	pigs.get( 0 ).setName( "One updated" );
	pigs.get( 1 ).setName( "Two updated" );
	return s.update( 10, pigs.toArray() );
} )