Fixed tests to work with current master

tests/PHPUnit/Integration/expected/test_Archive_InvalidationWebsite1_NewDataShouldAppear__VisitsSummary.get_month.xml

 <results>
     <result date="2010-03">
         <nb_uniq_visitors>2</nb_uniq_visitors>
+        <nb_users>1</nb_users>
         <nb_visits>2</nb_visits>
         <nb_actions>12</nb_actions>
         <nb_visits_converted>0</nb_visits_converted>

tests/PHPUnit/Integration/expected/test_Archive_InvalidationWebsite1_NewDataShouldNotAppear__VisitsSummary.get_month.xml

 <results>
     <result date="2010-03">
         <nb_uniq_visitors>1</nb_uniq_visitors>
+        <nb_users>1</nb_users>
         <nb_visits>1</nb_visits>
         <nb_actions>6</nb_actions>
         <nb_visits_converted>0</nb_visits_converted>

tests/PHPUnit/Integration/expected/test_Archive_InvalidationWebsite2_NewDataShouldAppear__VisitsSummary.get_month.xml

 <results>
     <result date="2010-01">
         <nb_uniq_visitors>2</nb_uniq_visitors>
+        <nb_users>1</nb_users>
         <nb_visits>2</nb_visits>
         <nb_actions>12</nb_actions>
         <nb_visits_converted>0</nb_visits_converted>

tests/PHPUnit/Integration/expected/test_Archive_InvalidationWebsite2_NewDataShouldNotAppear__VisitsSummary.get_month.xml

 <results>
     <result date="2010-01">
         <nb_uniq_visitors>1</nb_uniq_visitors>
+        <nb_users>1</nb_users>
         <nb_visits>1</nb_visits>
         <nb_actions>6</nb_actions>
         <nb_visits_converted>0</nb_visits_converted>