flow: Fix hypothetical memory leak in miniflow_move().

flow: Fix hypothetical memory leak in miniflow_move().

Ordinarily a miniflow will use its inline_values if its values can fit, but
there is nothing to prevent a small number of values from being stored
in malloc()'d memory.  If this happened, then miniflow_move() would leak
memory.  This commit fixes the problem.

This is a hypothetical problem.  I haven't seen it in practice.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>