devstack: fix rest-api typo

This fixes the cleanup for the rest-api since it was missing either '-'
or the '_'.

Change-Id: Id461458c6ba0045f28e9d26de11c318c5c4c51a4
Signed-off-by: Saul Wold <sgw@linux.intel.com>

devstack/lib/stx-fault

@@ -58,8 +58,8 @@ function cleanup_fault {
     if is_service_enabled fm-common; then
         cleanup_fm_common
     fi
-    if is_service_enabled fm-restapi; then
-        cleanup_fm_restapi
+    if is_service_enabled fm-rest_api; then
+        cleanup_fm_rest_api
     fi
 }