Modify default prefix assignment for Get LAN Config Params 56 & 59

The default prefix should be 0 for IPv6 addresses that are not
assigned. This permits the IPv6 address to be reported as "::/0"
instead of "::/128".

Tested:
'ipmitool raw 0xc 2 <nic> 56 0 0' run when the NIC has a DHCP
assigned address returns "::/0"
'ipmitool raw 0xc 2 <nic> 59 0 0' returns the prefix value assigned by
the DHCP server.

Change-Id: I82d0e44de9c30d858811f2e1dcabc98eb482cc77
Signed-off-by: Johnathan Mantey <johnathanx.mantey@intel.com>
diff --git a/transporthandler.cpp b/transporthandler.cpp
index 0aae64c..b2b7dce 100644
--- a/transporthandler.cpp
+++ b/transporthandler.cpp
@@ -507,7 +507,7 @@
     auto source = IPv6Source::Static;
     bool enabled = false;
     in6_addr addr{};
-    uint8_t prefix = AddrFamily<AF_INET6>::defaultPrefix;
+    uint8_t prefix{};
     auto status = IPv6AddressStatus::Disabled;
 
     auto ifaddr = channelCall<getIfAddr<AF_INET6>>(channel, set, origins);