Pipe the Docker registry password so that docker login doesn't block

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

CI was using a test of ! -s which appeared to give a false positive
and try to push when it shouldn't. I changed it to -z which checks
for an empty string instead.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

use golang 1.8.3 for gateway

Signed-off-by: Minh-Quan TRAN <account@itscaro.me>

Signed-off-by: Burton Rheutan <rheutan7@gmail.com>