Fix bugs preventing adding updated cache entries to the name hash

Fix bugs preventing adding updated cache entries to the name hash

Update replace_index_entry() to clear the CE_HASHED flag from the new cache
entry so that it can add it to the name hash in set_index_entry()

Fix refresh_cache_ent() to use the copy_cache_entry() macro instead of memcpy()
so that it doesn't incorrectly copy the hash state from the old entry.

Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>