Legacy UDP/TCP control protocols don't provide information about RTP
payload types, therefore don't pretend that we know that this is RTP.
Setting the RTP flag without knowing the payload types has the undesired
side effect that unknown payload types (all of them) would not be
handled by the kernel module.
Change-Id: I5882f777a5912b912ec7c870f21c77aac8127600
(cherry picked from commit e811cd474d)