Add start_dates to freezer and doc-ha

Both these meetings had inflight reviews at the begining of the year when we
added explict start_dates to all the yaml files.  This meant that they were
missed :(

It's a little hard to verify that these start dates are correct but looking at the irc-meetings.ics file the start date is set for:

Documentation HA Guide update Meeting: 2016-11-16
Freezer Meeting                      : 2016-11-10

So seomthing like:
---
 import datetime

 doc = (datetime.date(2016, 1, 27), datetime.date(2016, 11, 16))
 freezer  = (datetime.date(2016, 2, 11), datetime.date(2016, 11, 10))

 for start, end in [doc, freezer ]:
     print start
     for _ in range(52):
         d = start + datetime.timedelta(days=7*_)
         if d == end:
             print 'OK'
             break
     else:
             print 'Meeting doesn\'t match'
---

Shows that they seem to match.  The start dates were selected as the next
occurence after the merge of the approriate change
(I4f577786c473445d3e009b1979a236d78db15c39 and
I4287eca818a281a8eca78f8da7a07460f080cad7)

Change-Id: I3394c08a30de799989dae07a002226d60676ac3c

meetings/doc-ha-guide-update-meeting.yaml

@@ -6,6 +6,7 @@ schedule:
     day:        Wednesday
     irc:        openstack-meeting-3
     frequency:  biweekly-even
+    start_date: 20160127
 chair: Andrew Beekhof (beekhof)
 description:  >
   HA Guide update meeting.

meetings/freezer-meeting.yaml

@@ -6,6 +6,7 @@ schedule:
     day:        Thursday
     irc:        openstack-meeting-alt
     frequency:  weekly
+    start_date: 20160211
 chair: Guillermo Garcia (m3m0)
 description:  >
   The Freezer project team holds a weekly team meeting on IRC.