CA-235358: Fix AD users in child domains cannot log in to XenCenter 7
CA-235358: Fix AD users in child domains cannot log in to XenCenter 7

When user input username as "ChildDomain\Username", the original code
ignores "ChildDomain".

Signed-off-by: Liang Dai <b75e0c1afa1f3a887b91110b0d3218879b1a8933@citrix.com>

thomassa/xen-api,thomassa/xen-api,euanh/xen-api,srowe/xen-api,euanh/xen-api,Frezzle/xen-api,srowe/xen-api,srowe/xen-api,thomassa/xen-api,Frezzle/xen-api,euanh/xen-api,euanh/xen-api,thomassa/xen-api,Frezzle/xen-api,euanh/xen-api,Frezzle/xen-api,euanh/xen-api,srowe/xen-api,srowe/xen-api,Frezzle/xen-api,thomassa/xen-api,thomassa/xen-api