ShellPkg/Ifconfig6: Update error message and add a new line

If DAD failed, we print "It failed to set", print the IPv6
address and exit. We need a better error string
and also, after printing the IPv6 address, we need a new line
else the Shell> prompt will overwrite the IPv6 address. Fixed
these issues in this patch.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hegde Nagaraj P <nagaraj-p.hegde@hpe.com>
Reviewed-by: Sriram Subramanian <sriram-s@hpe.com>
Reviewed-by: Wu Jiaxin <jiaxin.wu@intel.com>

ShellPkg/Library/UefiShellNetwork2CommandsLib/Ifconfig6.c

@@ -2,6 +2,7 @@
   The implementation for Shell command IfConfig6.
 
   Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
+  (C) Copyright 2017 Hewlett Packard Enterprise Development LP<BR>
 
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
@@ -1490,6 +1491,7 @@ IfConfig6SetInterfaceInfo (
             &CfgManAddr[Index].Address,
             &CfgManAddr[Index].PrefixLength
             );
+          ShellPrintHiiEx (-1, -1, NULL, STRING_TOKEN (STR_IFCONFIG6_INFO_NEWLINE), gShellNetwork2HiiHandle);
         }
       }