Do not fail if address already exists

This patch fixes network uplink failures on Fedora 37 and Debian 11 VMs
with only one vCPU.  There is an underlying problem that causes the
script to be run more than once, but this patch is a workaround until
that bug can be found and fixed.

Fixes: QubesOS/qubes-issues#8305
Fixes: QubesOS/qubes-issues#8362

network/setup-ip

@@ -27,13 +27,13 @@ configure_network () {
     local secondary_dns="${10}"
     local custom="${11}"
 
-    /sbin/ip -- address add "$ip/$netmask" dev "$INTERFACE"
+    /sbin/ip -- address replace "$ip/$netmask" dev "$INTERFACE"
     if [[ "$custom" = false ]]; then
         /sbin/ip -- neighbour replace to "$gateway" dev "$INTERFACE" \
             lladdr "$netvm_mac" nud permanent
     fi
     if [ -n "$ip6" ]; then
-        /sbin/ip -- address add "$ip6/$netmask6" dev "$INTERFACE"
+        /sbin/ip -- address replace "$ip6/$netmask6" dev "$INTERFACE"
         if [[ "$custom" = false ]]; then
             /sbin/ip -- neighbour replace to "$gateway6" dev "$INTERFACE" \
                 lladdr "$netvm_mac" nud permanent