backend_init doesn't respect backend env variable

[williamcroberts]

The code below always initializes the backends no matter what the env variable returns.

CK_RV backend_init(void) {
    LOGV("Initializing backends");

    enum backend backend = get_backend();

    if (backend == backend_error) {
        return CKR_GENERAL_ERROR;
    }

    CK_RV rv = backend_fapi_init();
    if (rv) {
        static const char *msg = "FAPI backend was not initialized.";
        if (backend == backend_fapi) {
            LOGE(msg);
            return rv;
        }
        LOGW(msg);
    } else {
        fapi_init = true;
    }

    rv = backend_esysdb_init();
    if (rv) {
        LOGW("ESYSDB backend was not initialized.");
    } else {
        esysdb_init = true;
    }

    if (!fapi_init && !esysdb_init) {
        LOGE("Neither FAPI nor ESYSDB backends could be initialized.");
        return CKR_GENERAL_ERROR;
    }
    return CKR_OK;
}