Allow NULL pointer as UUID for attrib_db_update()
Allow NULL pointer as UUID for attrib_db_update()

A NULL uuid_t pointer means that the UUID should remain unchanged. This
simplifies most attrib_db_update() calls which do not change the
attribute UUID.

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