operator-sdk: privilege escalation due to incorrect permissions of /etc/passwd

Early versions of Operator-SDK provided an insecure method to allow operator containers to run in environments that used a random UID. Operator-SDK before 0.15.2 provided a script, user_setup, which modifies the permissions of the /etc/passwd file to 664 during build time. Developers who used Operator-SDK before 0.15.2 to scaffold their operator may still be impacted by this if the insecure user_setup script is still being used to build new container images. In affected images, the /etc/passwd file was created during build time with group-writable permissions and a group ownership of root (gid=0). An attacker who can execute commands within an affected container, even as a non-root user, may be able to leverage their membership in the root group to modify the /etc/passwd file. This could allow the attacker to add a new user with any arbitrary UID, including UID 0, leading to full root privileges within the container.