Concurrency verification behavior in QVL Impacted by QVE Policy

We have observed that the concurrency logic in QVL is being influenced by QVE policy. This behavior seems unintended and could lead to inconsistent handling of concurrent verifiction requests in QVL.

### Expected Behavior
The `qve_policy` is designed to impact QVE verification exclusively. Ideally, `qve_policy` should not affect the QVL's functionality.

### Current Behavior
Currently, QVL processes received verification requests **serially by default**. The default value of `qve_policy` is set to `SGX_QL_PERSISTENT` (which is equivalent to `SGX_QL_DEFAULT`). However, when we configure the `qve_policy` value to `SGX_QL_PERSISTENT_QVE_MULTI_THREAD`, QVL is capable of processing verification requests concurrently.

https://github.com/intel/SGXDataCenterAttestationPrimitives/blob/45554a754ba8c03342cc394831fa7f04db08805c/QuoteVerification/dcap_quoteverify/sgx_dcap_quoteverify.cpp#L504-L515