hlr.c: fix: also store the session state in read_cb_forward()

If the session state is not set (OSMO_GSUP_SESSION_STATE_NONE),
osmo_gsup_encode() would omit the OSMO_GSUP_SESSION_ID_IE.

Fix for Change-Id: Ia4f345abc877baaf0a8f73b8988e6514d9589bf5
Change-Id: Idcd209a59d1ee5230104f3101740140d366b0646
1 file changed