Rewrite the check of syncd is still running'

Author: pavel-shirshov

scripts/fast-reboot

@@ -44,8 +44,8 @@ docker kill teamd > /dev/null
 # Gracefully stop syncd
 docker exec -ti syncd /usr/bin/syncd_request_shutdown --cold > /dev/null
 
-# Check it was stopped
-until [[ $(docker top syncd | grep -q /usr/bin/syncd) -eq 0 ]]
+# Check that syncd was stopped
+while docker top syncd | grep -q /usr/bin/syncd
 do
   sleep 0.1
 done