Revert the early return from `parallel_rspec_runner.rb`

Signed-off-by: Rémy Coutable <remy@rymai.me>

tooling/lib/tooling/parallel_rspec_runner.rb

@@ -38,6 +38,12 @@ module Tooling
       Knapsack.logger.info tests_to_run
       Knapsack.logger.info
 
+      # Without this guard clause, we're run all the specs instead of none!
+      if tests_to_run.empty?
+        Knapsack.logger.info 'No tests to run on this node, exiting.'
+        return 0
+      end
+
       Process.wait Process.spawn(*rspec_command)
       Process.last_status.exitstatus
     end