Only cache the ubuntu image to make sure latest test image always built.
Only cache the ubuntu image to make sure latest test image always built.

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