Add missing barrier sync to rx placement infra code

Change-Id: I25ccf8260dbe7e1550aee3904a688fc135ce1f03
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vnet/interface_cli.c b/src/vnet/interface_cli.c
index e18a80f..d37c789 100644
--- a/src/vnet/interface_cli.c
+++ b/src/vnet/interface_cli.c
@@ -1445,8 +1445,10 @@
 /* *INDENT-OFF* */
 VLIB_CLI_COMMAND (cmd_set_if_rx_placement,static) = {
     .path = "set interface rx-placement",
-    .short_help = "set interface rx-placement <hw-interface> [queue <n>] [thread <n> | main]",
+    .short_help = "set interface rx-placement <hw-interface> [queue <n>] "
+      "[worker <n> | main]",
     .function = set_interface_rx_placement,
+    .is_mp_safe = 1,
 };
 
 /* *INDENT-ON* */