Relax a data formatter test

Before inspecting the contents of a list, make sure that we've stepped
past the push_back() that inserts the element we're interested in.

llvm-svn: 343899

lldb/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/list/TestDataFormatterLibcxxList.py

@@ -190,6 +190,7 @@ class LibcxxListDataFormatterTestCase(TestBase):
 
         self.runCmd("n") # This gets us past the printf
         self.runCmd("n")
+        self.runCmd("n")
 
         # check access-by-index
         self.expect("frame variable text_list[0]",