Merge #11259: Remove duplicate destination decoding
86e6dd4b6 Remove duplicate destination decoding (João Barbosa)
8d0041e60 Remove unused GetKeyID and IsScript methods from CBitcoinAddress (João Barbosa)
Pull request description:
Follow up of #11117, this patch removes an extra unnecessary destination decoding that was identified while reviewing #11117. It is also the only case where `IsValidDestinationString` is called before `DecodeDestination`.
For reference see [comment](https://github.com/bitcoin/bitcoin/pull/11117#discussion_r137145517).
Tree-SHA512: f5ff5cb28a576ccd819a058f102188bde55654f30618520cc680c91d2f6e536fe038fc7220dd2d2dd64c6175fcb23f89b94b48444521e11ddec0b2f8ef2c05dd