Drop centos 8 stream jobs

CentOS 8 Stream has reached its end of life and the upstream
package repos have been removed. The CentOS nodes from Zuul and
Nodepool are being removed. See the following email announcement:

https: //lists.opendev.org/archives/list/service-announce@lists.opendev.org/thread/YHPRWKWULKJATAJZPFIZCBHS7HZJE5V2/

Also, use libtool to run valgrind on executables, not wrapper scripts.
We can't be responsible for running down memory issues in bash or sed.

Co-Authored-By: Tim Burke <tim.burke@gmail.com>
Change-Id: I451b5d0a333ab1a7e3a372c27b4cde67397f3372

.zuul.yaml

@@ -13,14 +13,6 @@
       Build and run test and valgrind-test for liberasurecode
       on arm64.
 
-- job:
-    name: liberasurecode-unittests-centos-8-stream
-    parent: liberasurecode-unittests
-    nodeset: centos-8-stream
-    description: |
-      Build and run test and valgrind-test for liberasurecode.
-      This job runs on CentOS 8 Stream.
-
 - job:
     name: liberasurecode-unittests-centos-9-stream
     parent: liberasurecode-unittests
@@ -37,28 +29,17 @@
       Build and run test and valgrind-test for liberasurecode.
       This job runs on a FIPS-enabled CentOS 9 Stream system.
 
-- job:
-    name: liberasurecode-unittests-centos-8-stream-arm64
-    parent: liberasurecode-unittests
-    nodeset: centos-8-stream-arm64
-    description: |
-      Build and run test and valgrind-test for liberasurecode.
-      This job runs on CentOS 8 Stream on arm64.
-
 - project:
     check:
       jobs:
         - liberasurecode-unittests
-        - liberasurecode-unittests-centos-8-stream
         - liberasurecode-unittests-centos-9-stream
         - liberasurecode-unittests-centos-9-stream-fips
     check-arm64:
       jobs:
         - liberasurecode-unittests-arm64
-        - liberasurecode-unittests-centos-8-stream-arm64
     gate:
       jobs:
         - liberasurecode-unittests
-        - liberasurecode-unittests-centos-8-stream
         - liberasurecode-unittests-centos-9-stream
         - liberasurecode-unittests-centos-9-stream-fips

Makefile.am

@@ -51,6 +51,7 @@ test: check
 	@./test/test_xor_hd_code
 	@./test/libec_slap
  
+LIBTOOL_COMMAND = $(LIBTOOL) --mode execute
 VALGRIND_EXEC_COMMAND = $(LIBTOOL_COMMAND) valgrind --tool=memcheck \
 	--error-exitcode=1 --leak-check=yes --track-fds=yes \
 	--malloc-fill=A5 --free-fill=DE --fullpath-after=. --trace-children=yes