provision/docker: improve ExecuteCommand and ExecuteCommandOnce tests
provision/docker: improve ExecuteCommand and ExecuteCommandOnce tests

checking that the ExecuteCommand was called

ArxdSilva/tsuru,cezarsa/tsuru,guilhermebr/tsuru,cezarsa/tsuru,ggarnier/tsuru,ArxdSilva/tsuru,tsuru/tsuru,cezarsa/tsuru,guilhermebr/tsuru,ggarnier/tsuru,cezarsa/tsuru,ArxdSilva/tsuru,ggarnier/tsuru,tsuru/tsuru,tsuru/tsuru,tsuru/tsuru,guilhermebr/tsuru,gwmoura/tsuru,ggarnier/tsuru,gwmoura/tsuru,gwmoura/tsuru,ArxdSilva/tsuru,guilhermebr/tsuru