T1160: fix (ro|rw)community ACL

WHen building up the SNMP v2 community ro/rw access all hosts from
a INET version could access even when the community was locked to one
INET family.

Example #1:

set service snmp community bar network 172.16.0.0/12

Allowed access only to IPv4 network 172.16.0.0/12 but it allowed acces from
IPv6 ::/0.

Example #2:

set service snmp community baz network 2001:db8::/64

Limited IPv6 access to 2001:db8::/64 but IPv4 was open to 0.0.0.0/0