Formatting and comment updates in flow files

Some reformatting to meet coding standards.

Added a few comments to make it more clear where p->flow gets set.
dns: detect case of request flooding

In the case where DNS requests are sent over the same flow w/o a
reply being received, we now set an event in the flow and refuse
to add more transactions to the state. This protects the DNS
handling from getting overloaded slowing down everything.

A new option to configure this behaviour was added:

app-layer:
  protocols:
    dnsudp:
       enabled: yes
       detection-ports:
         udp:
           toserver: 53
       request-flood: 750

The request-flood parameter can be 0 (disabling this feature) or a
positive integer. It defaults to 500.

This means that if 500 unreplied requests are seen in a row an event
is set. Rule 2240007 was added to dns-events.rules to match on this.
DNS: trigger logging for toserver dir when previous reply is lost.
dns: fix transaction handling

When logging is disabled, the app layer would still be flagged
as logging. This caused transactions not to be freed until the
end of the flow as the logged tx id would never increment.

This fix postpones the setting of the app layer parser "logger"
flag to the point where we know the logger is enabled.
http & tls: fix transaction handling

When http and/or tls logging is disabled, the app layer would still
be flagged as logging. This caused transactions not to be freed until
the end of the flow as the logged tx id would never increment.

This fix postpones the setting of the app layer parser "logger"
flag to the point where we know the logger is enabled.