SquishTests: Make sure tst_git_local cleans up properly

Creator still writes gitProject.pro.user after cleanup() ran.

Change-Id: I78c8247090a7032b21ee3a763fd390bb16f3d24b
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

tests/system/suite_tools/tst_git_local/test.py

@@ -206,6 +206,7 @@ def main():
     test.compare(str(changed.plainText), "Retrieving data failed.",
                  "Showing an invalid commit can't succeed but Creator survived.")
     invokeMenuItem("File", "Exit")
+    waitForCleanShutdown()
 
 def deleteProject():
     path = os.path.join(srcPath, projectName)