provision/docker/docker.go: using getDockerServers on dockerCluster.
provision/docker/docker.go: using getDockerServers on dockerCluster.

Closes #673

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