Removes unnecessary elsif

Since the attribution is the same for both cases I think we can merge them.
Allow host to be set from the original event

This seems to be possible with other input types, so I thought it would
make sense here as well. Maybe I'm missing something?
[rabbitmq] March Hare 2.1.0+

[Release notes](http://blog.rubyrabbitmq.info/blog/2014/01/16/march-hare-2-dot-1-0-is-released/): nothing that may affect Logstash, though.
Merge pull request #965 from devin-c/udp_host

Allow host to be set from UDP input
Fix 'cleanup' step to properly delete all data.

In elasticsearch 1.0, the "DELETE /" request is now rejected by default.
So instead, we will "DELETE /*"
Merge pull request #951 from leandromoreira/patch-4

Removes unnecessary elsif
Merge pull request #971 from jordansissel/fix-es_http-tests-for-1.0

Fix 'cleanup' step to properly delete all data.
kv=cleanup
Restore the fitler thread safety check that was mysteriously lost, I think, in the new pipeline rewrite for 1.2.0 (LOGSTASH-1828)

Also mark the metrics filter as not threadsafe.
Include filter-worker validation before saying the config is good.
Merge pull request #981 from jordansissel/abort-on-not-threadsafe-filters

Restore the fitler thread safety check that was mysteriously lost, I thi...
Merge pull request #979 from kurtado/doc/filter/kv

kv=cleanup (docs improvements)
Merge pull request #970 from michaelklishin/patch-1

[rabbitmq] March Hare 2.1.0+