Make ipam_cidrs() return failure when call_weave fails

weave

@@ -788,7 +788,9 @@ ipam_cidrs() {
     IPAM_CIDRs=""
     if [ $# -eq 0 ] ; then
         # If no addresses passed in, get one in the default subnet
-        IPAM_CIDRS=$(call_weave POST /ip/$CONTAINER_ID)
+        if ! IPAM_CIDRS=$(call_weave POST /ip/$CONTAINER_ID) ; then
+            return 1
+        fi
         if [ "$IPAM_CIDRS" = "404 page not found" ] ; then
             echo "No IP address supplied (use the -iprange option on 'weave launch' to enable IP address allocation)" >&2
             return 1
@@ -798,9 +800,12 @@ ipam_cidrs() {
     while [ $# -gt 0 ] ; do
         if [ "${1%:*}" = "net" ] ; then
             if [ "$1" = "net:default" ] ; then
-                CIDR=$(call_weave POST /ip/$CONTAINER_ID)
+                IPAM_URL=/ip/$CONTAINER_ID
             else
-                CIDR=$(call_weave POST /ip/$CONTAINER_ID/"${1#net:}")
+                IPAM_URL=/ip/$CONTAINER_ID/"${1#net:}"
+            fi
+            if ! CIDR=$(call_weave POST $IPAM_URL) ; then
+                return 1
             fi
             if [ "$CIDR" = "404 page not found" ] ; then
                 echo "IP address allocation must be enabled to use --subnet (use the -iprange option on 'weave launch')" >&2