Enable schema1 support in configured registries

Many historically-published images in Quay.io use the schema1 format,
and both (oc image mirror) and (podman push) fail when pushing schema1
images to registries that reject schema1 (and even if they didn't fail,
the push would modify the manifest digest, which is inconsistent with
our disconnected operation design and the general desire to use
manifest digests for iamge references).

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

modules/installation-creating-mirror-registry.adoc

@@ -101,6 +101,7 @@ OpenSSL documentation.
      -v /opt/registry/certs:/certs:z \
      -e REGISTRY_HTTP_TLS_CERTIFICATE=/certs/domain.crt \
      -e REGISTRY_HTTP_TLS_KEY=/certs/domain.key \
+     -e REGISTRY_COMPATIBILITY_SCHEMA1_ENABLED=true \
      -d docker.io/library/registry:2
 ----
 <1> For `<local_registry_host_port>`, specify the port that your mirror registry

modules/ipi-install-creating-a-disconnected-registry.adoc

@@ -112,6 +112,7 @@ Replace `<user>` with the user name and `<passwd>` with the password.
   -e "REGISTRY_AUTH_HTPASSWD_PATH=/auth/htpasswd" \
   -e "REGISTRY_HTTP_TLS_CERTIFICATE=/certs/domain.crt" \
   -e "REGISTRY_HTTP_TLS_KEY=/certs/domain.key" \
+  -e "REGISTRY_COMPATIBILITY_SCHEMA1_ENABLED=true" \
   -v /opt/registry/data:/var/lib/registry:z \
   -v /opt/registry/auth:/auth:z \
   -v /opt/registry/certs:/certs:z \