Fix readerbookmark unit test

spec/unit/readerbookmark_spec.lua

@@ -197,7 +197,8 @@ describe("ReaderBookmark module", function()
             assert.are.same(15, readerui.bookmark:getNextBookmarkedPage(10))
         end)
         it("should search/add bookmarks properly #now", function()
-            DEBUG:turnOn()
+            -- clear bookmarks created by previous tests
+            readerui.bookmark.bookmarks = {}
             local p1 = { x = 0, y = 0, page = 100 }
             local bm1 = { notes = 'foo', page = 10,
                           pos0 = { x = 0, y = 0, page = 100 }, pos1 = p1, }