connection_write_to_buf: indirect recursion for CONN_TYPE_CONTROL

Call of connection_write_to_buf for CONN_TYPE_CONTROL allows immediate flush of the outbuf. Then if code tries to log something and control_event_logmsg is involved then it call of connection_write_to_buf recursively. Consequence calls blocked by ++disable_log_messages only then.

Three ways to fix:

1. Remove ability for immediate flush of the outbuf by connection_write_to_buf
2. Check in_connection_handle_write flag at start of connection_handle_write
3. Guard call of connection_handle_write by disable_control_logging and enable_control_logging

Every way have negative and positive impacts.