test/p_ossltest.c: check for return values in OSSL_PARAM_* calls

test/p_ossltest.c: check for return values in OSSL_PARAM_* calls

Some of the OSSL_PARAM_* calls haven't their return codes checked
(OSSL_PARAM_get_octet_string_ptr() call
in ossl_test_aes128cbchmacsha1_set_ctx_params(),
and OSSL_PARAM_set_size_t() call in drbg_ctr_get_ctx_params()),
and Coverity complained about it.  Add the missing checks.

Fixes: 032297054ab5 "Implement an ossltest provider to replace ossltest engine"
Resolves: https://github.com/openssl/project/issues/1618
Resolves: https://scan5.scan.coverity.com/#/project-view/65248/10222?selectedIssue=1665462
Resolves: https://scan5.scan.coverity.com/#/project-view/65248/10222?selectedIssue=1665463
Signed-off-by: Eugene Syromiatnikov <esyr@openssl.org>
Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/28583)