fflush: Split a temporary variable in two.

It is clearer to avoid reusing temporary variables for different
purposes.

Sponsored by: Klara, Inc.

(cherry picked from commit 1f90b4edffe815aebb35e74b79e10593b31f6b75)
(cherry picked from commit 1e99535be2ea9c0ef8bc57fc885e9c01fa95d2dd)
(cherry picked from commit ccdd8337f9cbd7d34e2e95df1440dd5f7225d0b4)