Support4Demos: Don't subscribe pages twice

Bug: 34334368
Test: Using Support4Demos, test the combination with the framework's MBS
Change-Id: I165a0bf1343f8816f961d272b7689e46488fc3c1
(cherry picked from commit 9a42cee4c6809fa365249d2d8a118bd00c12b0b1)
1 file changed