provision/docker/bs: fix assignment to nil map
provision/docker/bs: fix assignment to nil map

We should have a test for this method x)

hcxiong/tsuru,kgrvamsi/tsuru,tsuru/tsuru,kgrvamsi/tsuru,Endika/tsuru,ggarnier/tsuru,ArxdSilva/tsuru,ArxdSilva/tsuru,cezarsa/tsuru,kgrvamsi/tsuru,tsuru/tsuru,gciotta/tsuru,guilhermebr/tsuru,tsuru/tsuru,tuxmonteiro/tsuru,guilhermebr/tsuru,cezarsa/tsuru,guilhermebr/tsuru,gwmoura/tsuru,hcxiong/tsuru,cezarsa/tsuru,gwmoura/tsuru,ggarnier/tsuru,ArxdSilva/tsuru,guilhermebr/tsuru,Endika/tsuru,cezarsa/tsuru,gciotta/tsuru,hcxiong/tsuru,tuxmonteiro/tsuru,tuxmonteiro/tsuru,ArxdSilva/tsuru,Endika/tsuru,gciotta/tsuru,tsuru/tsuru,ggarnier/tsuru,gwmoura/tsuru,ggarnier/tsuru