Delete test files on the remote bucket

We are reverting the changes we did in #85, if we dont delete the files
the files can polute the bucket. So we will try to delete them and
ignore if it fails. Because in reality we only need the permission to
put an object for this plugin to correctly work.

Fixes: #97

Fixes #96

Author: ph

lib/logstash/outputs/s3.rb

@@ -258,6 +258,15 @@ def test_s3_write
 
     begin
       write_on_bucket(test_filename)
+
+      begin
+        remote_filename = "#{@prefix}#{File.basename(test_filename)}"
+        bucket = @s3.buckets[@bucket]
+        bucket.objects[remote_filename].delete
+      rescue StandardError => e
+        # we actually only need `put_object`, but if we dont delete them
+        # we can have a lot of tests files
+      end
     ensure
       File.delete(test_filename)
     end