display the top-level task start time as the build start time

We can't record the build start time in the database correctly for maven and windows builds, so show the task start time instead.

www/kojiweb/buildinfo.chtml

@@ -59,7 +59,7 @@
       </td>
     </tr>
     <tr>
-      <th>Started</th><td>$util.formatTimeLong($build.creation_time)</td>
+      <th>Started</th><td>$util.formatTimeLong($start_time)</td>
     </tr>
     #if $build.state == $koji.BUILD_STATES.BUILDING
     #if $estCompletion

www/kojiweb/index.py

@@ -1180,6 +1180,12 @@ def buildinfo(environ, buildID):
         if not values.has_key(field):
             values[field] = None
 
+    values['start_time'] = build['creation_time']
+    # the build start time is not accurate for maven and win builds, get it from the
+    # task start time instead
+    if mavenbuild or winbuild:
+        if task:
+            values['start_time'] = task['start_time']
     if build['state'] == koji.BUILD_STATES['BUILDING']:
         avgDuration = server.getAverageBuildDuration(build['package_id'])
         if avgDuration != None: