docker-setup: ensure ubuntu user exists
docker-setup: ensure ubuntu user exists

The default configuration uses ssh keys in the ubuntu user's $HOME.
Check if this user exists and create it (and the .ssh directory) if not.

cezarsa/tsuru,kgrvamsi/tsuru,ArxdSilva/tsuru,4eek/tsuru,tuxmonteiro/tsuru,hugoantunes/tsuru,mderaldo/tsuru,gciotta/tsuru,gwmoura/tsuru,4eek/tsuru,jblancett/tsuru,gwmoura/tsuru,hugoantunes/tsuru,guilhermebr/tsuru,tuxmonteiro/tsuru,firebitsbr/tsuru,Endika/tsuru,tsuru/tsuru,ArxdSilva/tsuru,RichardKnop/tsuru,cgvarela/tsuru,jblancett/tsuru,guilhermebr/tsuru,RichardKnop/tsuru,firebitsbr/tsuru,tuxmonteiro/tsuru,hcxiong/tsuru,ggarnier/tsuru,Endika/tsuru,cezarsa/tsuru,cezarsa/tsuru,4eek/tsuru,ggarnier/tsuru,mderaldo/tsuru,ggarnier/tsuru,gciotta/tsuru,hcxiong/tsuru,cgvarela/tsuru,firebitsbr/tsuru,guilhermebr/tsuru,cgvarela/tsuru,hcxiong/tsuru,jblancett/tsuru,cezarsa/tsuru,tsuru/tsuru,ArxdSilva/tsuru,kgrvamsi/tsuru,ggarnier/tsuru,Endika/tsuru,RichardKnop/tsuru,gciotta/tsuru,mderaldo/tsuru,gwmoura/tsuru,tsuru/tsuru,tsuru/tsuru,guilhermebr/tsuru,ArxdSilva/tsuru,kgrvamsi/tsuru