Don't use microseconds in NDB query
Don't use microseconds in NDB query

The method feed_utils.find_feeds_to_check() has been
broken for the past while. For some reason it only finds
feeds to check every few days. It should find each feed once
per day.

Oddly the queury works fine in unit tests.

The change sets microseconds to 0 in the variable passed to
ndb.gql() for last_checked. I thought this might be necessary
looking at the allowed values for dates in https://cloud.google.com/appengine/docs/standard/python/datastore/gqlreference#Syntax

  i.e. DATETIME(year, month, day, hour, minute, second)

Seems to work but needs monitoring over a few days.

adrian/feed2me,adrian/feed2me,adrian/feed2me