Update contrib scripts for Perfconf demo (#3363)

- Use --security-opt=label=disable to avoid problems with relabeling the ~/.ssh
  directory, since it disrupts the use of it from _outside_ the container.
- Switch the default container tag from `latest`  (which is the latest _release_)
  to `main`, because we haven't done a release build of the Agent since we
  updated the containerization.
- Move the generate-token invocation "first" in the demo script, to help fail
  early.
- Change the run-time from 20s to 5s.
- Add an explanatory comment to a bit of subtlety.

PBENCH-1115

contrib/containerized-pbench/pbench

@@ -24,7 +24,7 @@
 # these options and any others which the user has specified and passes in the
 # command to be executed.
 
-image_name=${PB_AGENT_IMAGE_NAME:-quay.io/pbench/pbench-agent-all-centos-8:latest}
+image_name=${PB_AGENT_IMAGE_NAME:-quay.io/pbench/pbench-agent-all-centos-8:main}
 config_file=${_PBENCH_AGENT_CONFIG:-${HOME}/.config/pbench/pbench-agent.cfg}
 pbench_run_dir=${PB_AGENT_RUN_DIR:-/var/tmp/${USER}/pbench-agent/run}
 pbench_server=${PB_AGENT_SERVER_LOC}
@@ -36,15 +36,14 @@ if [[ $# == 0 || $1 == "help" || $1 == "-h" || $1 == "--help" ]]; then
 fi
 
 if [[ -d "${HOME}/.ssh" && -r "${HOME}/.ssh" ]]; then
-    other_options="-v ${HOME}/.ssh:/root/.ssh:z ${other_options}"
+    other_options="--security-opt=label=disable -v ${HOME}/.ssh:/root/.ssh ${other_options}"
 fi
 
 if [[ -f "${config_file}" && -r "${config_file}" ]]; then
     other_options="-v ${config_file}:/opt/pbench-agent/config/pbench-agent.cfg:z ${other_options}"
 elif [[ -n "${pbench_server}" ]]; then
     echo "Warning:  the Pbench Agent config file is missing; attempting to generate one in ${config_file}" >&2
-    # TODO:  this should be handled by a separate Pbench Agent command which
-    #        provides a "configuration wizard".
+    # TODO:  this should be handled by a separate Pbench Agent "configuration wizard".
     mkdir -p $(dirname ${config_file})
     cat > ${config_file} <<- EOF
 		[DEFAULT]

contrib/containerized-pbench/pbench_demo

@@ -23,11 +23,13 @@ mkdir -p ${FIOTEST}
 #+
 # Run the demo!
 #-
+pbench pbench-generate-token --output=/var/lib/pbench-agent/.token
 pbench pbench-register-tool-set light
 pbench pbench-list-tools
 pbench pbench-user-benchmark --config example-workload -- \
     fio --directory=/fiotest --name fio_test_file --direct=1 --rw=randread \
-        --bs=16k --size=100M --numjobs=16 --time_based --runtime=20s \
+        --bs=16k --size=100M --numjobs=8 --time_based --runtime=5s \
         --group_reporting --norandommap
-pbench pbench-generate-token --output=/var/lib/pbench-agent/.token
-pbench pbench-results-move --token=$(< /var/tmp/pbench/pbench-agent/run/.token)
+# Note that the token file location below is evaluated -outside- the container,
+# unlike in the pbench-generate-token command above.
+pbench pbench-results-move --token=$(< /var/tmp/${USER}/pbench-agent/run/.token)