CIFS: Make cifsFileInfo_put work with strict cache mode
On strict cache mode when we close the last file handle of the inode we
should set invalid_mapping flag on this inode to prevent data coherency
problem when we open it again but it has been modified on the server.
Reviewed-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com> Signed-off-by: Steve French <sfrench@us.ibm.com>