This cache was added in b6b4967aa, when there was no real Zoom support.
With 63f349319, a proper identification of multimedia stream has been
added, making this cache quite useless: any improvements on Zoom
classification should be properly done in Zoom dissector.
Tested for some months with a few 10Gbits links of residential traffic: the
cache pretty much never returned a valid hit.
Avoid code duplication between these two protocols.
We remove support for RTCP over TCP; it is quite rare to find this kind
of traffic and, more important, we have never had support for RTP
over TCP: we should try to add both detecion as follow-up.
Fix a message log in the LINE code
