Show image pull output when using a builder image

[geoand]

Fixes: #6892

[gastaldi]

LGTM

[geoand]

I also verified manually that the output does show up.

Plus since we use docker builds in CI, one can always look there when it's done to see the expected output

[ia3andy]

@geoand I will test it in a few minutes ;-) thanks!!

[geoand]

@ia3andy you should see something like:

2020-01-31T07:17:19.8338408Z [INFO] [io.quarkus.deployment.pkg.steps.NativeImageBuildStep] Pulling image quay.io/quarkus/ubi-quarkus-native-image:19.3.1-java8
2020-01-31T07:17:21.0472365Z 19.3.1-java8: Pulling from quarkus/ubi-quarkus-native-image
2020-01-31T07:17:21.0481614Z 57de4da701b5: Pulling fs layer
2020-01-31T07:17:21.0500610Z cf0f3ebe9f53: Pulling fs layer
2020-01-31T07:17:21.0506723Z 74e4ceac2598: Pulling fs layer
2020-01-31T07:17:21.4158146Z cf0f3ebe9f53: Verifying Checksum
2020-01-31T07:17:21.4158656Z cf0f3ebe9f53: Download complete
2020-01-31T07:17:21.6920223Z 57de4da701b5: Verifying Checksum
2020-01-31T07:17:21.6921583Z 57de4da701b5: Download complete
2020-01-31T07:17:23.7386786Z 57de4da701b5: Pull complete
2020-01-31T07:17:23.8816428Z cf0f3ebe9f53: Pull complete
2020-01-31T07:17:24.9466170Z 74e4ceac2598: Verifying Checksum
2020-01-31T07:17:24.9467331Z 74e4ceac2598: Download complete
2020-01-31T07:17:39.8790892Z 74e4ceac2598: Pull complete

[ia3andy]

It works great! It looks like a small thing but it look less buggy now :) Very good job