smb: fix secondary channel creation issue with kerberos by populating hostname when adding channels

When mounting a share with kerberos authentication with multichannel
support, share mounts correctly, but fails to create secondary
channels. This occurs because the hostname is not populated when
adding the channels. The hostname is necessary for the userspace
cifs.upcall program to retrieve the required credentials and pass
it back to kernel, without hostname secondary channels fails
establish.

Cc: stable@vger.kernel.org
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Bharath SM <bharathsm@microsoft.com>
Reported-by: xfuren <xfuren@gmail.com>
Link: https://bugzilla.samba.org/show_bug.cgi?id=15824


Signed-off-by: Steve French <stfrench@microsoft.com>