add MockPageCacheRecycler in test jar

MockPageCacheRecycler is missing in test jar which makes failing tests when using
test jar in plugins:

```
1> [2014-01-11 10:51:30,531][ERROR][test                     ] FAILURE  : testWikipediaRiver(org.elasticsearch.river.wikipedia.WikipediaRiverTest)
  1> REPRODUCE WITH  : mvn test -Dtests.seed=5DAFD4FBAE587363 -Dtests.class=org.elasticsearch.river.wikipedia.WikipediaRiverTest -Dtests.method=testWikipediaRiver -Dtests.prefix=tests -Dtests.network=true -Dfile.encoding=MacRoman -Duser.timezone=Europe/Paris -Des.logger.level=INFO -Des.node.local=true -Dtests.cluster_seed=134842C2D806FFC0
  1> Throwable:
  1> java.lang.NoClassDefFoundError: org/elasticsearch/cache/recycler/MockPageCacheRecycler
  1>     org.elasticsearch.test.cache.recycler.MockPageCacheRecyclerModule.configure(MockPageCacheRecyclerModule.java:30)
  1>     org.elasticsearch.common.inject.AbstractModule.configure(AbstractModule.java:60)
```