api/app: checking unit by machine number, instead of instance id
api/app: checking unit by machine number, instead of instance id

Fix #100.

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