Fix sudo command in skipper-entrypoint.sh

skipper/data/skipper-entrypoint.sh

@@ -28,12 +28,12 @@ if ! [ -z "${SKIPPER_DOCKER_GID}" ];then
      usermod -G root ${SKIPPER_USERNAME}
   fi
 
-  if ! which sudo > /dev/null; then
-    su -m ${SKIPPER_USERNAME} -c "$@"
-  else
-    # for debian dsitros (maybe for others too) -m flag resets the PATH variable
+  if sudo -l -U ${SKIPPER_USERNAME} > /dev/null; then
+    # for debian distros (maybe for others too) -m flag resets the PATH variable
     # so we need to use sudo -E to preserve the PATH
     sudo -sE -u ${SKIPPER_USERNAME} "$@"
+  else 
+    su -m ${SKIPPER_USERNAME} -c "$@"
   fi
 else
   bash -c "$@"