systests: auto-update: minor cleanup

- use PODMAN_TMPDIR, not BATS_TMPDIR, for temp file
- in teardown, do not assume that SNAME_FILE will exist
  (test could fail before that file gets created)
- remove "?" ("ignore exit status") from rmi & prune.
  Probably holdovers from the days before -f. If
  these commands fail even with -f, we need to know.

Signed-off-by: Ed Santiago <santiago@redhat.com>

test/system/255-auto-update.bats

@@ -8,14 +8,17 @@ load helpers.network
 load helpers.registry
 load helpers.systemd
 
-SNAME_FILE=$BATS_TMPDIR/services
+export SNAME_FILE
 
 function setup() {
     skip_if_remote "systemd tests are meaningless over remote"
     basic_setup
+
+    SNAME_FILE=${PODMAN_TMPDIR}/services
 }
 
 function teardown() {
+    if [[ -e $SNAME_FILE ]]; then
         while read line; do
             if [[ "$line" =~ "podman-auto-update" ]]; then
                 echo "Stop timer: $line.timer"
@@ -28,7 +31,10 @@ function teardown() {
         done < $SNAME_FILE
 
         rm -f $SNAME_FILE
-    run_podman '?' rmi -f                            \
+    fi
+    SNAME_FILE=
+
+    run_podman rmi -f                              \
             quay.io/libpod/alpine:latest           \
             quay.io/libpod/busybox:latest          \
             quay.io/libpod/localtest:latest        \
@@ -37,7 +43,7 @@ function teardown() {
 
     # The rollback tests may leave some dangling images behind, so let's prune
     # them to leave a clean state.
-    run_podman '?' image prune -f
+    run_podman image prune -f
     basic_teardown
 }