test_sample_set.rb delete, select by info, not by index.

Found another crappy test thanks to random order. In some cases, the
patient needed for the edit test was being deleted before the test could
execute. So selecting a specific patient for the delete test should make
things more robust.

server/web2py/applications/vidjil/tests/functional/test_sample_set.rb

@@ -103,7 +103,8 @@ class TestSampleSet < BrowserTest
 
     count = table.tbody.rows.count
     # click delete button for first line in table
-    table.i(:class => "icon-erase", :index => 1).click
+    line = table.td(:text => /test patient 4/).parent
+    line.i(:class => "icon-erase").click
 
     delete_button = $b.button(:text => "delete")
     delete_button.wait_until_present