How to manually change OpenShift's default image streams credentials

Issue

• Need to change credentials in OpenShift for external registry registry.redhat.io;

• Can't use any default image streams from namespace openshift. Pods using them stays in status ErrImagePull and/or ImagePullBackOff. Detailed error shows:

  Failed to pull image "docker-registry.default.svc:5000/openshift/mariadb@sha256:c14bc6d18c0cb79d1deab12ccdef16cb2a43615133689e86e9d58d155d34618a": rpc error: code = Unknown desc = Error reading manifest sha256:c14bc6d18c0cb79d1deab12ccdef16cb2a43615133689e86e9d58d155d34618a in docker-registry.default.svc:5000/openshift/mariadb: unknown: unable to pull manifest from registry.redhat.io/rhscl/mariadb-102-rhel7:latest: Get https://registry.redhat.io/v2/rhscl/mariadb-102-rhel7/manifests/sha256:c14bc6d18c0cb79d1deab12ccdef16cb2a43615133689e86e9d58d155d34618a: unauthorized: Please login to the Red Hat Registry using your Customer Portal credentials. Further instructions can be found here: https://access.redhat.com/articles/3399531