MDL-51285 mod_forum: Discussion post should not have same time stamp

Discussion post are sorted by timemodified
if they have same timemodified then results
will be random

mod/forum/tests/behat/discussion_navigation.feature

@@ -78,21 +78,26 @@ Feature: A user can navigate to previous and next discussions
     And I add a new discussion to "Test forum name" forum with:
       | Subject | Discussion 1 Group 0 |
       | Message | Test post message |
+    And I wait "1" seconds
     And I add a new discussion to "Test forum name" forum with:
       | Subject | Discussion 2 Group 0 |
       | Message | Test post message |
+    And I wait "1" seconds
     And I add a new discussion to "Test forum name" forum with:
       | Subject | Discussion 1 Group 1 |
       | Message | Test post message |
       | Group   | Group 1 |
+    And I wait "1" seconds
     And I add a new discussion to "Test forum name" forum with:
       | Subject | Discussion 2 Group 1 |
       | Message | Test post message |
       | Group   | Group 1 |
+    And I wait "1" seconds
     And I add a new discussion to "Test forum name" forum with:
       | Subject | Discussion 1 Group 2 |
       | Message | Test post message |
       | Group   | Group 2 |
+    And I wait "1" seconds
     And I add a new discussion to "Test forum name" forum with:
       | Subject | Discussion 2 Group 2 |
       | Message | Test post message |