Bump go to v1.21.6 and set a single source of truth (#10926)

build/run-in-docker.sh

@@ -76,12 +76,7 @@ fi
 
 USER=${USER:-nobody}
 
-#echo "..printing env & other vars to stdout"
-#echo "HOSTNAME=`hostname`"
-#uname -a
-#env
-#echo "DIND_ENABLED=$DOCKER_IN_DOCKER_ENABLED"
-#echo "done..printing env & other vars to stdout"
+USE_SHELL=${USE_SHELL:-"/bin/bash"}
 
 if [[ "$DOCKER_IN_DOCKER_ENABLED" == "true" ]]; then
   echo "..reached DIND check TRUE block, inside run-in-docker.sh"
@@ -100,5 +95,5 @@ else
     args="$args -v /var/run/docker.sock:/var/run/docker.sock"
   fi
 
-  ${RUNTIME} run $args ${E2E_IMAGE} /bin/bash -c "${FLAGS}"
-fi
+  ${RUNTIME} run $args ${E2E_IMAGE} ${USE_SHELL} -c "${FLAGS}"
+fi