Only add rhel base repos when REG_REPOS is not set

For offline (satellite based) installs the base repos won't be
available and the base packages will come from a different named repo
in satellite which will be specified by REG_REPOS.

This change will ensure no base repos are added when REG_REPOS are
specified so offline image builds are possible. All required base
repos need to be added to REG_REPOS when it is used. Documentation[1]
already includes base repos, so this should not be disruptive.

[1] https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/16.1/html/director_installation_and_usage/creating-whole-disk-images#disk-image-environment-variables

Change-Id: Iafb81d50dffdac40d3b011670200b8da4c3a58f0

diskimage_builder/elements/rhel-common/README.rst

@@ -104,6 +104,8 @@ A single string representing a list of repository names separated by a
 comma (No spaces).  Each of the repositories in this string are enabled
 through subscription manager.  Once you've attached a subscription, you can
 find available repositories by running subscription-manager repos --list.
+No base repos will be added when REG_REPOS is set, so these must be included
+in REG_REPOS.
 
 #### REG\_SERVER\_URL
 Gives the hostname of the subscription service to use. The default is

diskimage_builder/elements/rhel-common/pre-install.d/00-rhel-registration

@@ -10,15 +10,17 @@ set -o pipefail
 opts=
 attach_opts=
 arch=$(uname -m)
+repos="repos "
+base_repos=
 
 if [ "${DIB_RELEASE:-7}" == "7" ]; then
-    repos="repos --enable rhel-7-server-rpms"
+    base_repos="rhel-7-server-rpms"
     satellite_repo="rhel-7-server-rh-common-rpms"
 elif [ "${DIB_RELEASE}" == "8" ]; then
     if [ -n "${REG_RELEASE:-}" ]; then
-        repos="repos --enable rhel-8-for-${arch}-appstream-eus-rpms --enable rhel-8-for-${arch}-baseos-eus-rpms"
+        base_repos="rhel-8-for-${arch}-appstream-eus-rpms rhel-8-for-${arch}-baseos-eus-rpms"
     else
-        repos="repos --enable rhel-8-for-${arch}-appstream-rpms --enable rhel-8-for-${arch}-baseos-rpms"
+        base_repos="rhel-8-for-${arch}-appstream-rpms rhel-8-for-${arch}-baseos-rpms"
     fi
     satellite_repo="satellite-tools-6.5-for-rhel-8-${arch}-rpms"
 fi
@@ -93,6 +95,10 @@ if [ -n "${REG_REPOS:-}" ]; then
     for repo in $(echo $REG_REPOS | tr ',' '\n'); do
         repos="$repos --enable $repo"
     done
+else
+    for repo in $base_repos; do
+        repos="$repos --enable $repo"
+    done
 fi
 
 if [ -n "${REG_TYPE:-}" ]; then