For new built layers, it can be pushed into remote registry. However, it
might not be pulled as base layer. Before this commit, the dist repo
source label for mountFrom call only is updated at pull stage. Without
mountFrom, it will take long time to push existing layers which can be
mountFrom. Based on this case, we should update dist repo source after
pushing layer successfully.
Signed-off-by: Wei Fu <fuweid89@gmail.com>
1845c31ee7