Ignore future dates

If an entry arrives with a date in the future, disregard the date
and use the internal fetch date instead.

Note, the ignore_entry option is not safe to use without this patch:
  rubys/venus#35

Change-Id: If2c6ea31c8d60211e93615c6104d193e1970e271

planet.ini

@@ -18,6 +18,7 @@ cache_directory = cache
 output_dir      = /srv/planet/openstack
 feed_timeout    = 20
 items_per_page  = 60
+future_dates    = ignore_date
 log_level       = DEBUG
 
 # additional files to copy (note the wildcards!)