prevent proxy from interferring with weave run

...which could result in containers unexpectedly getting multiple IP
addresses.

Fixes #1279.

test/680_proxy_weave_run_test.sh

@@ -0,0 +1,16 @@
+#! /bin/bash
+
+. ./config.sh
+
+C1=10.2.1.13
+
+start_suite "Start containers with 'weave run' via proxy"
+
+weave_on $HOST1 launch
+weave_on $HOST1 launch-proxy
+
+proxy start_container $HOST1 $C1/24 --name=c1
+# check we get exactly one IP back, the one specified
+assert "weave_on $HOST1 ps c1 | cut -d ' ' -f 3-" $C1/24
+
+end_suite