Describe the feature:
Hi,
I found 'too many files open' problem in my ES enviroment. And I use the commad ls -al /proc/ES_PID/fd , found that ES opened particularly large number of translog files.
After some search on this problem , I tried to restart a runing normally ES (6.6.1). I found that ，every time ES is restarted, there will be one more translog file on some shards. And all the translogs have no operation data, like below( The server time is incorrect，but I don't think it's concern ):

Elasticsearch version (bin/elasticsearch --version):
Version: 6.6.1, Build: default/tar/1fd8f69/2019-02-13T17:10:04.160291Z, JVM: 1.8.0_60
Plugins installed: []
No Plugins
JVM version (java -version):
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
OS version (uname -a if on a Unix-like system):
Centos 7.6
Linux 3.10.0-957.5.1.el7.x86_64 #1 SMP Fri Feb 1 14:54:57 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Description of the problem including expected versus actual behavior:
Empty translog files(no operation data) keep increasing.
Old translog exist beyond 12 hours(index.translog.retention.age = 12h).
I think empty translog files should be deleted or don't creat new translog files.
Steps to reproduce:
restart ES node
Please include a minimal but complete recreation of the problem, including
(e.g.) index creation, mappings, settings, query etc. The easier you make for
us to reproduce it, the more likely that somebody will take the time to look at it.

1. defautl index setting as follow:
   "settings":{ "index.number_of_replicas":"0", "index.refresh_interval":"10s", "index.number_of_shards":"1", "index.routing.allocation.require.tag":"hot", "index.indexing.slowlog.level": "info", "index.indexing.slowlog.threshold.index.trace": "500ms", "index.indexing.slowlog.threshold.index.debug": "2s", "index.indexing.slowlog.threshold.index.info": "5s", "index.indexing.slowlog.threshold.index.warn": "10s", "index.search.slowlog.level": "info", "index.search.slowlog.threshold.fetch.trace": "200ms", "index.search.slowlog.threshold.fetch.debug": "500ms", "index.search.slowlog.threshold.fetch.info": "800ms", "index.search.slowlog.threshold.fetch.warn": "1s", "index.search.slowlog.threshold.query.trace": "500ms", "index.search.slowlog.threshold.query.debug": "2s", "index.search.slowlog.threshold.query.info": "5s", "index.search.slowlog.threshold.query.warn": "10s", "index.translog.durability": "async", "index.translog.flush_threshold_size": "5000mb", "index.translog.sync_interval": "120s", "index.mapping.ignore_malformed": true }
2. Auto create index use the dynamic mapping, and index name is created by date, only the index created today is active. Indices created before today have no data to index.
3. Restart ES, the translog of indices created before today (no data to index) keep increasing

If I missed some configuration， please let me know.
I'd be happy to provide additional details, whatever is needed.

Thanks!