ZOOKEEPER-5009: Memory Leak in zoo_sasl_client_create

[nihiragarwal24]

Fix memory leak in zoo_sasl_client_create on failure

zoo_sasl_client_create allocates a zoo_sasl_client_t and then duplicates several strings. If any duplication fails (e.g. due to OOM), the function calls zoo_sasl_client_destroy(sc) and returns NULL.

However, zoo_sasl_client_destroy only frees internal members and does not free the structure itself, resulting in a memory leak on every failed initialization attempt.

Impact: Repeated SASL initialization retries under transient allocation failures can cause unbounded memory growth and eventual OOM.

Fix: Explicitly free the allocated structure in the error path.

zoo_sasl_client_destroy(sc);
free(sc);
return NULL;