[rb] fix bug with driver logging

the io accessor for the process sets a default value, so assigning with ||= operator will never work

Author: titusfortner

rb/lib/selenium/webdriver/common/service_manager.rb

@@ -80,8 +80,8 @@ def uri
       def build_process(*command)
         WebDriver.logger.debug("Executing Process #{command}", id: :driver_service)
         @process = ChildProcess.build(*command)
-        @process.io = @io
-        @process.io ||= WebDriver.logger.io if WebDriver.logger.debug?
+        @io ||= WebDriver.logger.io if WebDriver.logger.debug?
+        @process.io = @io if @io
 
         @process
       end