stream_srv: osmo_stream_srv_get_ofd() works only in OSMO_FD mode

The corresponding client function osmo_stream_cli_get_ofd()
already contained an OSMO_ASSERT, but the server side was missing
this so far.  The 'ofd' member only has meaning in the context
of OSMO_FD, so calling that function from generic code is wrong!

Change-Id: I50df259040e011135a31fe1aee231eba430fa94a
Fixes: Change-Id I2f52c7107c392b6f4b0bf2a84f8c873c084a200c
Related: OS#5753
---
M src/stream_srv.c
1 file changed, 17 insertions(+), 0 deletions(-)

diff --git a/src/stream_srv.c b/src/stream_srv.c
index 1370e42..36e21cc 100644
--- a/src/stream_srv.c
+++ b/src/stream_srv.c
@@ -834,6 +834,7 @@
 struct osmo_fd *
 osmo_stream_srv_get_ofd(struct osmo_stream_srv *conn)
 {
+	OSMO_ASSERT(conn->mode == OSMO_STREAM_MODE_OSMO_FD);
 	return &conn->ofd;
 }
 

