Revert the date cache feature as it somehow (cause: unknown) causing …

…pageviews to be lost when importing big log files.

This particular log file I'm testing on is for an intranet with thousands times the same IP address. Not sure if it's related, but the same IP address will have many visits at the same second, for different users (different _id=X in the piwik.php requests)
refs matomo-org/matomo#300

import_logs.py

@@ -47,13 +47,7 @@
             print >> sys.stderr, 'simplejson (http://pypi.python.org/pypi/simplejson/) is required.'
             sys.exit(1)
 
-try:
-    from collections import OrderedDict
-except ImportError:
-    try:
-        from ordereddict import OrderedDict
-    except ImportError:
-        pass
+
 
 ##
 ## Constants.
@@ -1556,10 +1550,6 @@ def invalid_line(line, reason):
         resolver.check_format(format)
 
         hits = []
-        try:
-            cache_dates = OrderedDict()
-        except NameError:
-            cache_dates = None
         for lineno, line in enumerate(file):
             try:
                 line = line.decode(config.options.encoding)
@@ -1585,7 +1575,6 @@ def invalid_line(line, reason):
                 is_robot=False,
                 is_error=False,
                 is_redirect=False,
-                date=None,
                 args={},
             )
 
@@ -1640,38 +1629,24 @@ def invalid_line(line, reason):
             # Parse date.
             # We parse it after calling check_methods as it's quite CPU hungry, and
             # we want to avoid that cost for excluded hits.
-            if cache_dates is not None:
-                # To mitigate CPU usage, parsed dates are cached.
-                try:
-                    timezone_key = format.get('timezone')
-                except BaseFormatException:
-                    timezone_key = ''
-                date_key = (format.get('date'), timezone_key)
-                hit.date = cache_dates.get(date_key)
-            if not hit.date:
-                date_string = format.get('date')
-                try:
-                    hit.date = datetime.datetime.strptime(date_string, format.date_format)
-                except ValueError:
-                    invalid_line(line, 'invalid date')
-                    continue
-
-                # Parse timezone and substract its value from the date
-                try:
-                    timezone = float(format.get('timezone'))
-                except BaseFormatException:
-                    timezone = 0
-                except ValueError:
-                    invalid_line(line, 'invalid timezone')
-                    continue
+            date_string = format.get('date')
+            try:
+                hit.date = datetime.datetime.strptime(date_string, format.date_format)
+            except ValueError:
+                invalid_line(line, 'invalid date')
+                continue
 
-                if timezone:
-                    hit.date -= datetime.timedelta(hours=timezone/100)
+            # Parse timezone and substract its value from the date
+            try:
+                timezone = float(format.get('timezone'))
+            except BaseFormatException:
+                timezone = 0
+            except ValueError:
+                invalid_line(line, 'invalid timezone')
+                continue
 
-                if cache_dates is not None:
-                    if len(cache_dates) > 3600:
-                        cache_dates.popitem(False)
-                    cache_dates[date_key] = hit.date
+            if timezone:
+                hit.date -= datetime.timedelta(hours=timezone/100)
 
             if config.options.replay_tracking:
                 # we need a query string and we only consider requests with piwik.php