Drop clients from proxy_worker, not proxy_conn

[cottsay]

A previous refactor moved the authorization process from the proxy_conn to the proxy_worker, but did not introduce any mechanism to drop an in-progress authorization before a client connection was assigned to an available proxy_conn for normal use. Because ownership of the client connection was also moved to the proxy_worker, it's safe to initiate the connection dropping process from the proxy_worker instead of the proxy_conn, which will cover the in-progress authorization case as well.

This was previously done with a borrowed reference to the client connection here:

openelp/src/proxy_conn.c

Lines 850 to 860 in 11fde32

	void proxy_conn_drop(struct proxy_conn_handle *pc)
	{
	struct proxy_conn_priv *priv = pc->priv;
	mutex_lock_shared(&priv->mutex_client);
	if (priv->conn_client != NULL)
	conn_drop(priv->conn_client);
	mutex_unlock_shared(&priv->mutex_client);
	}