Use ContainerID when restarting a container

Otherwise, we are risking to leak DNS entries which happens when
ContainerName is passed to `weave reset` and subsequent internal call
to nameserver creates a new entry instead of replacing the old one.
The ContainerID of the new entry is set to ContainerName and in such case
stopping the container will not remove the new entry.

test/100_cross_hosts_2_test.sh

@@ -30,6 +30,8 @@ assert_raises "exec_on $HOST1 c5 $PING $C6"
 # check that restart retains the same IP, and reclaims it in IPAM
 weave_on $HOST2 restart c6
 assert_raises "exec_on $HOST1 c5 $PING $C6"
+# check that restart does not create any additional DNS entry
+assert "weave_on $HOST2 report -f \"{{len .DNS.Entries}}\"" "6"
 sleep 31 # past the IPAM timeout
 start_container $HOST2 net:$SUBNET_2 --name=c7
 C7=$(container_ip $HOST2 c7)

weave

@@ -2179,8 +2179,8 @@ EOF
         for CIDR in $ALL_CIDRS ; do
             call_weave PUT /ip/$CONTAINER/$CIDR?check-alive=true
         done
-        with_container_netns_or_die $1 attach $ALL_CIDRS
-        when_weave_running with_container_fqdn $1 put_dns_fqdn $ALL_CIDRS
+        with_container_netns_or_die $CONTAINER attach $ALL_CIDRS
+        when_weave_running with_container_fqdn $CONTAINER put_dns_fqdn $ALL_CIDRS
         echo $RES
         ;;
     dns-add)