CI build/push failures on tfserving-proxy image are not included in exit values

[RafalSkolasinski]

User reported that seldonio/tfserving-proxy_rest:1.2.3 is not present on the Docker Hub.
The post 1.2.3 nightly and dev builds are present.

It looks like there was an issue in the CI build. It failed on building the related GRPC image

seldon-core/jenkins-x/logs/SeldonIO/seldon-core/release-1.2.3/1.log

Line 10574 in e9a48f7

ERROR: An error occurred: context deadline exceeded

but this was not caught by the exit values so went unnoticed

seldon-core/jenkins-x/logs/SeldonIO/seldon-core/release-1.2.3/1.log

Lines 11297 to 11303 in e9a48f7

	Python exit value: 0
	Operator exit value: 0
	Engine exit value: 0
	Executor exit value: 0
	Mock model exit value: 0
	Alibi Detect exit value: 0
	Request Logger exit value: 0

Extra context:

• CI build script is here

  seldon-core/ci_build_and_push_images.sh

  Lines 118 to 124 in c6df020

  	function build_push_tfproxy {
  	make \
  	-C integrations/tfserving \
  	build_all \
  	push_all
  	TFPROXY_EXIT_VALUE=$?
  	}

• Related Makefile targets are here:

  seldon-core/integrations/tfserving/Makefile

  Lines 20 to 24 in c6df020

  	.PHONY: build_all
  	build_all: build_rest build_grpc
  	.PHONY: push_all
  	push_all: push_rest push_grpc

[RafalSkolasinski]

Actually, I was initially wrong. The pipeline failed

seldon-core/jenkins-x/logs/SeldonIO/seldon-core/release-1.2.3/1.log

Line 11305 in e9a48f7

Pipeline failed on stage 'build-and-push' : container 'step-build-and-push-images'. The execution of the pipeline has stopped.�[0m

because the related exit value is included, it just not get printed in logs

seldon-core/ci_build_and_push_images.sh

Line 184 in c6df020

+ ${TFPROXY_EXIT_VALUE} \