logstash: Parse apache2 events where day of month < 10

The date format used in the apache2 log stream pads the day of month
field of it's timestamp with spaces rather than zeros or leaving the
value as a variable width string. The logstash grok filter we were using
previously did not account for the space padding. Also adds date parsing
support for the space padded dates.

The changeset also corrects an obvious typo in the date format for fatal
events.

Bug:60772
Change-Id: I0546094fb0a3fb266515e2aeeb55ba7b303b560c