Don't overflow item refcount on get

Counts as a miss if the refcount is too high. ASCII multigets are the only
time refcounts can be held for so long.

doing a dirty read of refcount. is aligned.

trying to avoid adding an extra refcount branch for all calls of item_get due
to performance. might be able to move it in there after logging refactoring
simplifies some of the branches.
static void bin_list_sasl_mechs(conn *c) {
    if (!settings.sasl) {
        write_bin_error(c, PROTOCOL_BINARY_RESPONSE_UNKNOWN_COMMAND, NULL,
                        c->binary_header.request.bodylen
                        - c->binary_header.request.keylen);
        return;
    }

    init_sasl_conn(c);
    const char *result_string = NULL;
    unsigned int string_length = 0;
    int result=sasl_listmech(c->sasl_conn, NULL,
                             "",   /* What to prepend the string with */
                             " ",  /* What to separate mechanisms with */
                             "",   /* What to append to the string */
                             &result_string, &string_length,
                             NULL);
    if (result != SASL_OK) {
        /* Perhaps there's a better error for this... */
        if (settings.verbose) {
            fprintf(stderr, "Failed to list SASL mechanisms.\n");
        }
        write_bin_error(c, PROTOCOL_BINARY_RESPONSE_AUTH_ERROR, NULL, 0);
        return;
    }
    write_bin_response(c, (char*)result_string, 0, 0, string_length);
}

static void bin_list_sasl_mechs(conn *c) {
    if (!settings.sasl) {
        write_bin_error(c, PROTOCOL_BINARY_RESPONSE_UNKNOWN_COMMAND, NULL,
                        c->binary_header.request.bodylen
                        - c->binary_header.request.keylen);
        return;
    }

    init_sasl_conn(c);
    const char *result_string = NULL;
    unsigned int string_length = 0;
    int result=sasl_listmech(c->sasl_conn, NULL,
                             "",   /* What to prepend the string with */
                             " ",  /* What to separate mechanisms with */
                             "",   /* What to append to the string */
                             &result_string, &string_length,
                             NULL);
    if (result != SASL_OK) {
        /* Perhaps there's a better error for this... */
        if (settings.verbose) {
            fprintf(stderr, "Failed to list SASL mechanisms.\n");
        }
        write_bin_error(c, PROTOCOL_BINARY_RESPONSE_AUTH_ERROR, NULL, 0);
        return;
    }
    write_bin_response(c, (char*)result_string, 0, 0, string_length);
}
