fix bad return value in dhcp_do_request_*

1. bad return status make it return uninitialized prefixLength with a magic
number in android_net_utils_runDhcpCommon()
2. it will make DhcpInfoInternal.makeLinkAddress() to throw
IllegalArgumentException when try to connect a Wifi AP
3. the exception will make system reboot, of cource it random.

Change-Id: Iabc0cd5b69c1316f4eeae0aa1b8a91444dca4562
Signed-off-by: Michael Wu <michaelstay@gmail.com>

libnetutils/dhcp_utils.c

@@ -367,9 +367,8 @@ int dhcp_do_request_renew(const char *interface,
         return -1;
     }
     if (strcmp(prop_value, "ok") == 0) {
-        fill_ip_info(interface, ipaddr, gateway, prefixLength,
+        return fill_ip_info(interface, ipaddr, gateway, prefixLength,
                 dns1, dns2, server, lease, vendorInfo);
-        return 0;
     } else {
         snprintf(errmsg, sizeof(errmsg), "DHCP Renew result was %s", prop_value);
         return -1;