Fixing problematic bok_choy test

By moving the team_page.first_member_username access to occur before
click_first_profile_image() is called, we avoid a potential issue
where the wrapper() method defined in page_object.py, which
decorates the property, calls into _verify_page() and raises a
WrongPageError.

common/test/acceptance/tests/lms/test_teams.py

@@ -954,9 +954,11 @@ class TeamPageTest(TeamsTabBase):
         self._set_team_configuration_and_membership()
         self.team_page.visit()
 
+        learner_name = self.team_page.first_member_username
+
         self.team_page.click_first_profile_image()
 
-        learner_profile_page = LearnerProfilePage(self.browser, self.team_page.first_member_username)
+        learner_profile_page = LearnerProfilePage(self.browser, learner_name)
         learner_profile_page.wait_for_page()
         learner_profile_page.wait_for_field('username')
         self.assertTrue(learner_profile_page.field_is_visible('username'))