pgstat_reset_remove_files ignores its argument

in 9.3 and 9.4, pgstat_reset_remove_files uses the global variable
pgstat_stat_directory rather than the argument it is passed, "directory".
On crash recovery, this means the tmp directory gets cleared twice and the
permanent pg_stat doesn't get cleared at all.

It seems like the obvious one line change would fix it, but I haven't
tested it because I don't know how to cause a crash without pg_stat already
being empty.

pgstat_reset_remove_files(const char *directory)
{
DIR *dir;
struct dirent *entry;
char fname[MAXPGPATH];

dir = AllocateDir(pgstat_stat_directory);

Cheers,

Jeff