Valgrind : Leak Check / DRD : UTransportMockTest possible mem leak, and data race

[BishrutSubedi]

To reproduce locally:

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

Tool: LEAK CHECK
------------------------
FAILURE DETECTED: ==156385== ERROR SUMMARY: 4 errors from 4 contexts (suppressed: 0 from 0)

Tool: DRD
------------------------
FAILURE DETECTED: ==156681== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

==146334== LEAK SUMMARY:
==146334==    definitely lost: 0 bytes in 0 blocks
==146334==    indirectly lost: 0 bytes in 0 blocks
==146334==      possibly lost: 868 bytes in 27 blocks
==146334==    still reachable: 43,006 bytes in 548 blocks
==146334==         suppressed: 0 bytes in 0 blocks
==146334== 
==146334== For lists of detected and suppressed errors, rerun with: -s
==146334== ERROR SUMMARY: 4 errors from 4 contexts (suppressed: 0 from 0)