Install from prestaged ostree_repo if exists in

/opt/platform-backup

To make installation more efficient, we need to prestage the
ostree_repo in /opt/platform-backup.

When we add a subcloud, the ostree_repo will not be fetched from
the System Controller, but from the prestaged ostree_repo, if it
exists.

Test Plan:
PASS: Verify that the ostree_repo is not pulled from the system
      controller but from /opt/platform-backup for installation.

Story: 2010120
Task: 46691
Change-Id: I6a00b28abe96f5d254a77331fc231cd9edac7bea
Signed-off-by: Shrikumar Sharma <shrikumar.sharma@windriver.com>

kickstart/files/miniboot.cfg

@@ -1920,6 +1920,23 @@ else
         repo="${PHYS_SYSROOT}/var/www/pages/feed/rel-xxxPLATFORM_RELEASExxx/ostree_repo"
         mkdir -p "${repo}"
 
+        # If we have already prestaged ostree_repo in /opt/platform-backup,
+        # then we should use that repo instead of downloading off of the system controller.
+
+        backup_device=/dev/disk/by-partlabel/platform_backup
+        backup_mount=/tmp/platform-backup
+
+        ilog "Temporary backup mount is ${backup_mount}"
+        mkdir -p "${backup_mount}"
+        mount "${backup_device}" "${backup_mount}" 2>/dev/null
+
+        # If ostree_repo is found at the mounted backup directory,
+        # then set the ostree url to its location.
+        if [ -e ${backup_mount}/ostree_repo ]; then
+            insturl="file:///${backup_mount}/ostree_repo"
+            ilog "Setting insturl to ${insturl} to use prestaged ostree_repo"
+        fi
+
         # Tell LAT to install from this local stage
         # i.e. override where LAT installs from.
         export instl=${repo}
@@ -1947,6 +1964,8 @@ else
         if [ $rc -ne 0 ]; then
             report_failure_with_msg "ostree pull failed, rc=$rc"
         fi
+
+        umount ${backup_mount}
         umount ${PHYS_SYSROOT}
 
     fi