AddToWallet implies BindWallet

Now that AddToWallet is called when loading transactions from the
wallet database, BindWallet can be integrated into that and does not
need to be an extra step.

Leaves behaviour unchanged, but makes the
fFromLoadWallet/!fFromLoadWallet paths in AddToWallet a bit more
symmetric.
Merge pull request #3701

09ec3af AddToWallet implies BindWallet (Wladimir J. van der Laan)