msc_ho: fix CALL IDENTIFIER in HANDOVER REQUEST

When msc_ho_send_handover_request() generates the HANDOVER REQUEST
message, it does not populate the call_id struct member.

In ran_msg_a.c the struct member call_id is used, but the
call_id_present flag is not set, which also prevents the call_id being
added to the message

Change-Id: I6b1b55b3f5a3092d9557dc2512020c766a9ff744
Related: OS#4582
diff --git a/src/libmsc/ran_msg_a.c b/src/libmsc/ran_msg_a.c
index e6dee52..ab58526 100644
--- a/src/libmsc/ran_msg_a.c
+++ b/src/libmsc/ran_msg_a.c
@@ -1121,6 +1121,7 @@
 
 		.imsi = n->imsi,
 		.codec_list_msc_preferred = n->codec_list_msc_preferred,
+		.call_id_present = n->call_id_present,
 		.call_id = n->call_id,
 		.global_call_reference = n->global_call_reference,
 		.global_call_reference_len = n->global_call_reference_len,