Fix SC2181 ("[ $?") outside tests/

Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12042

contrib/dracut/02zfsexpandknowledge/module-setup.sh.in

@@ -17,8 +17,7 @@ get_pool_devices() {
   local prefix
   local resolved
   poolconfigtemp=`mktemp`
-  @sbindir@/zpool list -v -H -P "$1" > "$poolconfigtemp" 2>&1
-  if [ "$?" != "0" ] ; then
+  if ! @sbindir@/zpool list -v -H -P "$1" > "$poolconfigtemp" 2>&1 ; then
     poolconfigoutput=$(cat "$poolconfigtemp")
     dinfo "zfsexpandknowledge: pool $1 cannot be listed: $poolconfigoutput"
   else