afr: fix possble memory leaks in rename

[zhangxyue]

when one brick goes down, memory leaks after rename.

rename after one brick offline:
afr_changelog_do
AFR_ENTRY_RENAME_TRANSACTION
AFR_ENTRY_TRANSACTION

afr_changelog_cbk(..., cookie = i, xattr = dict1)
changelog_xdata[i] = dict_ref(dict1); // dict1 ref=2
afr_changelog_cbk(..., cookie = i, xattr = dict2) // second
changelog_xdata[i] = dict_ref(dict2); // without unref dict1

[ThalesBarretto]

do you have a statedump or a reproducer?

[zhangxyue]

do you have a statedump or a reproducer?

1、create 3*1 replicate volume, and start volume
2、shutdown one brick of them,and then do rename via fuse-daemon
3、statedump fuse-daemon, you can find dict_t、data_pair_t、data_t active-count is growing