protocol: fix problem with line break and OSMUX

The SDP parameter block must be detached from the regular parameters
using an additional line break (empty line). At the moment this works
because the empty OSMOX variable is added and by this also adds a
line break. It breaks as soon as OSMUX is used again.

- Make clear that no OSMUX variable is added when OSMUX is not in
  use.

- Add the extra line break independently

Change-Id: I6261971040db527b96fe79676520ccd7794bd327
1 file changed