TESTCASES: Fix Coverity finding: Using uninitialized value

1. Defect type: UNINIT
1. opencryptoki-3.27.0/testcases/crypto/rsa_func.c:2367:5: var_decl: Declaring variable "oaep_params" without initializer.
48. opencryptoki-3.27.0/testcases/crypto/rsa_func.c:2648:13: uninit_use: Using uninitialized value "oaep_params.hashAlg".
49. opencryptoki-3.27.0/testcases/crypto/rsa_func.c:2648:13: uninit_use: Using uninitialized value "oaep_params.mgf".
#  2646|                                           NULL, &cipher_len, NULL);
#  2647|           if (rc != CKR_OK) {
#  2648|->             if (rc == CKR_MECHANISM_PARAM_INVALID &&
#  2649|                   encaps_mech.mechanism == CKM_RSA_PKCS_OAEP &&
#  2650|                   is_ep11_token(slot_id) &&

diff -up opencryptoki-3.27.0/testcases/crypto/rsa_func.c.orig opencryptoki-3.27.0/testcases/crypto/rsa_func.c
--- opencryptoki-3.27.0/testcases/crypto/rsa_func.c.orig	2026-07-22 14:10:57.771848322 +0200
+++ opencryptoki-3.27.0/testcases/crypto/rsa_func.c	2026-07-22 16:00:07.212999532 +0200
@@ -2364,7 +2364,7 @@ CK_RV do_EncapsDecapsRSA(struct GENERATE
     CK_BYTE_PTR cipher = NULL;
     CK_ULONG cipher_len;
     CK_MECHANISM encaps_mech, mech;
-    CK_RSA_PKCS_OAEP_PARAMS oaep_params;
+    CK_RSA_PKCS_OAEP_PARAMS oaep_params = {0};
     CK_BYTE clear[32], encypted[32], re_cipher[32];
     CK_ULONG encrypted_len = 32, re_cipher_len = 32;