travis: remove some noise and try to drop memory usage
travis: remove some noise and try to drop memory usage

Getting some OOM errors in the tip and Go 1.5 builds, I'm trying to fix
them.

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