I couldnt find quickly which erratum can be responsible for the changed behaviour but there are some UCR variables.
Example taken from a 4.1 system:
# ucr search samba | grep interface
If this variable is set to 'yes', Samba only listens to requests on the network interfaces specified in the variable 'samba/interfaces'. If the variable is unset, Samba listens on all interfaces.
If the variable 'samba/interfaces/bindonly' is set to 'yes', Samba only binds to the interfaces listed in this variable. Multiple entries need to be separated by blanks.
This variable defines network interfaces which are ignored by samba (e.g. eth0). Multiple values need to be separated by blanks.