network: Remove dead code getting, but not using ipdef

The fetch of 'ipdef' in networkRefreshDhcpDaemon() when the loop to fill
in ipv4def fails to find an ipv4 address with dhcp defined. The filled in
ipdef value was not used.  Code was made unnecessary with commit it 2d5cd1.

src/network/bridge_driver.c

@@ -1156,9 +1156,6 @@ networkRefreshDhcpDaemon(struct network_driver *driver,
         if (!ipv4def && (ipdef->nranges || ipdef->nhosts))
             ipv4def = ipdef;
     }
-    /* If no IPv4 addresses had dhcp info, pick the first (if there were any). */
-    if (!ipdef)
-        ipdef = virNetworkDefGetIpByIndex(network->def, AF_INET, 0);
 
     ipv6def = NULL;
     for (ii = 0;