cifs: fix filp leak in cifs_atomic_open()

commit dfb1d61b0e9f9e2c542e9adc8d970689f4114ff6 upstream.

If an error occurs after having called finish_open() then fput() needs to
be called on the already opened file.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>