obexd: Fix regression when calling obc_session_shutdown within callback
obexd: Fix regression when calling obc_session_shutdown within callback

Commit c07ddfbd019d3545cce2d7ec694143cdc55a2167 introduced the freeing of
the active pending request on obc_session_shutdown without checking if
the request was already processed/terminated.

pkarasev3/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,silent-snowman/bluez,pkarasev3/bluez,silent-snowman/bluez,mapfau/bluez,ComputeCycles/bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,silent-snowman/bluez,silent-snowman/bluez,mapfau/bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez