DAOS-14440 build: Update distro versions in GHA (#13608)

The supported distro versions got missed in 56e3228 for the GitHub
Actions workflow.

Signed-off-by: Brian J. Murrell <brian.murrell@intel.com>

.github/workflows/rpm-build-and-test.yml

@@ -5,10 +5,10 @@ env:
   #       build is done on the lowest version and test on the highest with a "sanity test"
   #       stage done on all versions in the list ecept the highest
   EL8_BUILD_VERSION: 8.6
-  EL8_VERSION: 8
+  EL8_VERSION: 8.8
   EL9_BUILD_VERSION: 9
   EL9_VERSION: 9
-  LEAP15_VERSION: 15.4
+  LEAP15_VERSION: 15.5
 
 on:
   workflow_dispatch:

ci/functional/test_main.sh

@@ -45,7 +45,7 @@ test_cluster() {
         FIRST_NODE=${first_node}                        \
         TEST_RPMS=${TEST_RPMS}                          \
         NODELIST=${tnodes}                              \
-        BUILD_URL=\"$BUILD_URL\"                        \
+        BUILD_URL=\"${BUILD_URL:-Unknown in GHA}\"      \
         STAGE_NAME=\"$STAGE_NAME\"                      \
         $(cat ci/functional/test_main_prep_node.sh)"
 }