osbuilder: Stop skopeo being installed by default

With the new rust image pull service skopeo we can parameterise whether to build
and install skopeo and turn it off by default if we don't need
signature verification support

Fixes: #3170

Signed-off-by: stevenhorsman <steven@uk.ibm.com>

tools/osbuilder/scripts/lib.sh

@@ -219,11 +219,16 @@ ${extra}
 	  agent-is-init-daemon: "${AGENT_INIT}"
 EOT
 
-	if [ "${SKOPEO_UMOCI}" = "yes" ]; then
+	if [ "${SKOPEO}" = "yes" ]; then
 		cat >> "${file}" <<-EOF
 	skopeo:
 	  url: "${skopeo_url}"
 	  version: "${skopeo_branch}"
+EOF
+	fi
+
+	if [ "${UMOCI}" = "yes" ]; then
+		cat >> "${file}" <<-EOF
 	umoci:
 	  url: "${umoci_url}"
 	  version: "${umoci_tag}"