WORKDIR ignores the currently set USER and creates the new directories
with the root user ownership.
This changes that, by executing a chown after the mkdir if needed, and
also handle the case where the provided USER is an uid and the passwd
file is not available to resolve to the username.
Fixes#2259
Signed-off-by: Aris Buzachis <buzachis.aris@gmail.com>
Signed-off-by: Aris Buzachis <buzachis.aris@gmail.com>