tests/unit/test-util-sockets: fix mem-leak on error object

tests/unit/test-util-sockets: fix mem-leak on error object

The test fails with --enable-asan as the error struct is never freed.
In the case where the test expects a success but it fails, let's also
report the error for debugging (it will be freed internally).

Fixes 316e8ee8d6 ("util/qemu-sockets: Refactor inet_parse() to use QemuOpts")

Signed-off-by: Matheus Tavares Bernardino <matheus.bernardino@oss.qualcomm.com>
Reviewed-by: Juraj Marcin <jmarcin@redhat.com>
Message-ID: <518d94c7db20060b2a086cf55ee9bffab992a907.1748280011.git.matheus.bernardino@oss.qualcomm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>