Valgrind : Leak Check / DRD : PublisherSubscriberTest possible memleak

[BishrutSubedi]

To reproduce locally:

bash lint/valgrind.sh build/Release/bin/PublisherSubscriberTest

==145606== LEAK SUMMARY:
==145606==    definitely lost: 0 bytes in 0 blocks
==145606==    indirectly lost: 0 bytes in 0 blocks
==145606==      possibly lost: 411 bytes in 13 blocks
==145606==    still reachable: 33,135 bytes in 423 blocks
==145606==         suppressed: 0 bytes in 0 blocks
==145606== 
==145606== For lists of detected and suppressed errors, rerun with: -s
==145606== ERROR SUMMARY: 4 errors from 4 contexts (suppressed: 0 from 0)