smpp: fix vlr_subscr use count bugs

In smpp_openbsc.c submit_to_sms(), "get" the appropriate use count upon
assigning sms->receiver, fixing a -1 use count upon sms_free().

Also, avoid a "put" of a NULL subscriber in the same function.

Related: OS#3930
Change-Id: Idaf01cd3cfa08088ce0d543d0576db957dc94262
1 file changed