TS-2168: Use #ifdef to control reclaimable freelist options

1) Define reclaimabe freelist options only when compiles ATS
   with --enable-reclaimabe-freelist,

2) "proxy.config.allocator.enable_reclaim" will set to 1 in
   RecordsConfig.cc by default, so that it will keep consistent
   with records.config.default.in when enable reclaimable freelist.

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>