Why bitcoind does not respect rpcbind for testnet?
I still have no idea as to WHY this is happening. But changing config to this:

[main]
# Allow JSON-RPC connections from, by default only localhost are allowed
rpcbind=127.0.0.1
rpcbind=10.18.0.1
rpcallowip=127.0.0.1
rpcallowip=10.18.0.0/24

[test]
# Use the test chain
testnet=1

rpcbind=127.0.0.1
rpcbind=10.18.0.1
rpcallowip=127.0.0.1
rpcallowip=10.18.0.0/24


Solved the issue

admin@az-bitcoind:~$ sudo netstat -natp | grep 8332
tcp        0      0 10.18.0.1:8332          0.0.0.0:*               LISTEN      566/bitcoind        
tcp        0      0 127.0.0.1:8332          0.0.0.0:*               LISTEN      566/bitcoind        
tcp        0      0 10.18.0.1:18332         0.0.0.0:*               LISTEN      567/bitcoind        
tcp        0      0 127.0.0.1:18332         0.0.0.0:*               LISTEN      567/bitcoind     


No idea why I have to duplicate this settings. I assumed that as long as [main] or [test] are not specified, all config options apply in general