Use alpine image for nginx
Use alpine image for nginx

Signed-off-by: Soedarsono <7b04db74b92806048807a678e76e75c693e4041d@gmail.com>

angry-tony/Portus-20170827,SUSE/Portus,angry-tony/Portus-20170827,angry-tony/Portus-20170827,angry-tony/Portus-20170827,SUSE/Portus,mssola/Portus,mssola/Portus,SUSE/Portus,mssola/Portus,SUSE/Portus,mssola/Portus