Always sync database addresses when persisting returned index.
Always sync database addresses when persisting returned index.

This fixes lookup errors or missing details of addresses returned by
getnewaddress and account branch extensions performed by
accountsyncaddressindex.

jrick/dcrwallet,jrick/btcwallet,jrick/dcrwallet,decred/dcrwallet,jrick/btcwallet,decred/dcrwallet