DAPI: Calls to `getTransaction` only valid if wallet is loaded

[kxcd]

https://github.com/dashpay/platform/blob/ed354ca52969676f8231765fc04bbe02b1d9ba25/packages/dapi/lib/externalApis/dashcore/rpc.js#L174-L193

Where is is this getting called? A masternode does not have an attached wallet, so calling this on an MN will return the empty set and an error. IMO these two methods should be removed.