server/mqttd: fix two memory leaks

[bagder]

No description provided.

[dfandrich]

Analysis of PR #15290 at 0db4f680:

Test http/test_17_ssl_use.py::TestSSLUse::test_17_09_ssl_min_max[TLSv1-0--2] failed, which has NOT been flaky recently, so there could be a real issue in this PR.

Test http/test_17_ssl_use.py::TestSSLUse::test_17_09_ssl_min_max[TLSv1-0--1] failed, which has NOT been flaky recently, so there could be a real issue in this PR.

Test http/test_17_ssl_use.py::TestSSLUse::test_17_09_ssl_min_max[TLSv1-0-0] failed, which has NOT been flaky recently, so there could be a real issue in this PR.

Test http/test_17_ssl_use.py::TestSSLUse::test_17_09_ssl_min_max[TLSv1-1--2] failed, which has NOT been flaky recently, so there could be a real issue in this PR.

Test http/test_17_ssl_use.py::TestSSLUse::test_17_09_ssl_min_max[TLSv1-1--1] failed, which has NOT been flaky recently, so there could be a real issue in this PR.

Test http/test_17_ssl_use.py::TestSSLUse::test_17_09_ssl_min_max[TLSv1-1-0] failed, which has NOT been flaky recently, so there could be a real issue in this PR.

Test http/test_17_ssl_use.py::TestSSLUse::test_17_09_ssl_min_max[TLSv1-2--2] failed, which has NOT been flaky recently, so there could be a real issue in this PR.

There are more failures, but that's enough from Gha.

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