Fix memory leaks with DNS and Net tests

With reference to (WRT) https://github.com/apache/trafficserver/pull/855, on line no. 74 of 'test_P_DNS.cc' there is a memory leak and on line no. 72 of 'test_P_Net.cc' there is memory leak – both memory leaks are errors.

Ping zwoop

Found by https://github.com/bryongloden/cppcheck