Build from Docker Distribution fork and update to v2.7.4-gitlab

v2.7.2-gitlab has the patch to enable MD5 checksums on top of v2.7.1. This change is done for a number of reasons:

1. To prepare for future changes in the GitLab Container Registry
2. To get the version number right (e.g. v2.7.2-gitlab instead of v2.7.1.m)
3. To make the build consistent with the one used by the cloud-native container.

v2.7.3-gitlab updates the storage driver to use the latest Google SDK: container-registry!2 (merged)

v2.7.4-gitlab fixes an issues with v2.7.3-gitlab with non-default Google credentials: container-registry!7 (merged)

This registry upgrade hopefully will fix 0-byte upload issues: https://github.com/googleapis/google-cloud-go/issues/746