ensure selenium specs always wait for requests for context modules

Fixes an issue in context module specs where Selenium wasn't waiting for
a link to appear before clicking it. The link it was trying to click is
hidden or displayed based on an AJAX request, so it was sometimes
unavailable.

test plan:
  - ensure specs pass.

Change-Id: Ifc88b07ba18c50bbe1297ad1f65a2278aff4ab1f
Reviewed-on: https://gerrit.instructure.com/17740
Reviewed-by: Shawn Meredith <shawn@instructure.com>
QA-Review: Shawn Meredith <shawn@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>

Author: Stanley Stuart

spec/selenium/context_modules_spec.rb

@@ -47,6 +47,8 @@ def create_modules(number_to_create)
 
       get "/courses/#{@course.id}/modules"
 
+      # button appears after ajax requests
+      wait_for_ajaximations
       f('.module_progressions_link').click
       wait_for_ajaximations
       f(".student_list").should be_displayed
@@ -78,6 +80,7 @@ def create_modules(number_to_create)
       get "/courses/#{@course.id}/modules"
 
       #opens the student progression link and validates all modules have no information"
+      wait_for_ajaximations
       f('.module_progressions_link').click
       wait_for_ajaximations