integration: fix panic on gce detroy when it's not initialized
integration: fix panic on gce detroy when it's not initialized

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