Lock onto ubuntu 16.04 to allow builds on docker cloud.
Lock onto ubuntu 16.04 to allow builds on docker cloud.

trungdtbk/faucet,mwutzke/faucet,gizmoguy/faucet,trungdtbk/faucet,trentindav/faucet,anarkiwi/faucet,gizmoguy/faucet,anarkiwi/faucet,trentindav/faucet,faucetsdn/faucet,faucetsdn/faucet,shivarammysore/faucet,wackerly/faucet,REANNZ/faucet,mwutzke/faucet,REANNZ/faucet,shivarammysore/faucet,wackerly/faucet