cifs: fix confusing debug message

Since rc was initialised to -ENOMEM in cifs_get_smb_ses(), when an
existing smb session was found, free_xid() would be called and then
print

  CIFS: fs/cifs/connect.c: Existing tcp session with server found
  CIFS: fs/cifs/connect.c: VFS: in cifs_get_smb_ses as Xid: 44 with uid: 0
  CIFS: fs/cifs/connect.c: Existing smb sess found (status=1)
  CIFS: fs/cifs/connect.c: VFS: leaving cifs_get_smb_ses (xid = 44) rc = -12

Fix this by initialising rc to 0 and then let free_xid() print this
instead

  CIFS: fs/cifs/connect.c: Existing tcp session with server found
  CIFS: fs/cifs/connect.c: VFS: in cifs_get_smb_ses as Xid: 14 with uid: 0
  CIFS: fs/cifs/connect.c: Existing smb sess found (status=1)
  CIFS: fs/cifs/connect.c: VFS: leaving cifs_get_smb_ses (xid = 14) rc = 0

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>