[api] Make source controller test more reliable

test_get_project_meta_history relies on no other test writing to
kde4/_project, but that's not guaranteed. So replace the hard coded
rev=1 with the revision we have before the actual test runs

The underlying reason is that attribute creation and deletion now
stores _attributes in the model (which was lost in cases before)

src/api/test/functional/source_controller_test.rb

@@ -1739,6 +1739,10 @@ def test_get_project_meta_history
     get '/source/kde4/_project/_history?meta=1'
     assert_response :success
     assert_xml_tag(tag: 'revisionlist')
+    # remember the current HEAD so we can check it later
+    # value depends on the test order
+    rl = Xmlhash.parse(@response.body)
+    oldrevision = rl.elements('revision').last['rev']
     get '/source/kde4/_meta'
     assert_response :success
     oldmeta = @response.body
@@ -1762,7 +1766,7 @@ def test_get_project_meta_history
     get '/source/kde4/_project/_meta?meta=1'
     assert_response :success
     assert_xml_tag(tag: 'project')
-    get '/source/kde4/_project/_meta?meta=1&rev=1'
+    get "/source/kde4/_project/_meta?meta=1&rev=#{oldrevision}"
     assert_response :success
     assert_xml_tag(tag: 'project')
     assert_xml_tag(tag: 'title', content: 'blub') # fixture string