provision/docker: simplify test for the DockerProvisioner.Destroy
provision/docker: simplify test for the DockerProvisioner.Destroy

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