path_openat(): fix double fput()

path_openat() jumps to the wrong place after do_tmpfile() - it has
already done path_cleanup() (as part of path_lookupat() called by
do_tmpfile()), so doing that again can lead to double fput().

Cc: stable@vger.kernel.org	# v3.11+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
