Fix download of lower layer rpms

A recent change to centralize the conversion of
URL to CENGN mirror URL was converting some URL's
incorrectly.   It should not convert a URL that is
already a CENGN url.

Closes-bug: 2029499
Signed-off-by: Scott Little <scott.little@windriver.com>
Change-Id: I7c94d5542c26e83b8a08d8f72d007dff971322ee

centos-mirror-tools/url_utils.sh

@@ -239,6 +239,12 @@ CENGN_HOST="mirror.starlingx.cengn.ca"
 CENGN_PORT="80"
 CENGN_URL_ROOT="mirror"
 
+to_regex () {
+    # Currently only care about one case
+    # convert '.' to '[.]'
+    echo $1 | sed 's#[.]#[.]#g'
+}
+
 url_to_stx_mirror_url () {
     local URL="$1"
     local DISTRO="$2"
@@ -250,6 +256,11 @@ url_to_stx_mirror_url () {
         return 1
     fi
 
+    if [[ ${URL} =~ $(to_regex ${CENGN_HOST}) ]]; then
+        echo "${URL}"
+        return 0
+    fi
+
     FS_PATH="$(repo_url_to_sub_path "$URL")"
     if [ $? -ne 0 ]; then
         >&2 echo "Error: $FUNCNAME (${LINENO}): repo_url_to_sub_path '$URL'"