In https://github.com/btcsuite/btcwallet/pull/419#issuecomment-212482492
I mentioned that btcwallet should wait until btcd also switches back
to upstream package paths so that duplicate packages are not included
in and bloat the btcwallet binary. Even while btcd has not yet
switched to the upstream flags package, this change can still be made
now since it is only used by btcd's main package, which is not
included in btcwallet.
