raop: Add back initial volume RTSP SET_PARAMETER request on connect

raop: Add back initial volume RTSP SET_PARAMETER request on connect

Regression introduced in commit 8c6407f:
raop: Merge TCP and UDP code paths + refactoring

Anyway, we need to determine if initial volume has to be setup before
sending RECORD or after:

- Setting it up *before* shouldn't be a problem: sink.c waits for
CONNECT state, set the volume and client.c triggers RECORD only once
he's got the SET_PARAMETER reply from server.

- Setting it up *after* seems to be more difficult if we try not to
send any audio before receiving the SET_PARAMETER reply form server. A
solution may be to send SET_PARAMETER just after the RECORD server
response is received and hope that it get processed by server during the
2sec latency/buffering time...

Attached patch implement that last solution. Works for me, but I cannot
guaranty it will with your hardware...