mesh: Fixes Config client send publish message
When Config client model send publish message, app_idx will
be need, however, currently code clear this value use `&`,
this will be generate error when app_idx not zero.
@@ -1265,7 +1265,7 @@ static int mod_pub_set(u16_t net_idx, u16_t addr, u16_t elem_addr,
net_buf_simple_add_le16(msg, elem_addr);
net_buf_simple_add_le16(msg, pub->addr);
- net_buf_simple_add_le16(msg, (pub->app_idx & (pub->cred_flag << 12)));
+ net_buf_simple_add_le16(msg, (pub->app_idx | (pub->cred_flag << 12)));
net_buf_simple_add_u8(msg, pub->ttl);
net_buf_simple_add_u8(msg, pub->period);
net_buf_simple_add_u8(msg, pub->transmit);
