Pluginkey hashmap not emptied after crypto_read failure

[stze]

I've noticed, in parse_cb function in connection.c, that if a message could not be decrypted correctly and the client closes the connection, that the client can not connect again because the pluginkey hashmap entry is not deleted.

After the client closes the connection a call to free_connection is missing. This means, the connection reference count is wrong in case a message could not be decrypted.