In some cases, we were calling `mbedtls_test_ssl_endpoint_free()` on an
uninitialized `mbedtls_test_ssl_endpoint` object if the test case failed
early, e.g. due to `psa_crypto_init()` failing. This was largely harmless,
but could have caused weird test results in case of failure, and was flagged
by Coverity.
Use a more systematic style for initializing the stack object as soon as
it's declared.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
0038408f55