Merge #11277: Fix uninitialized URI in batch RPC requests

Merge #11277: Fix uninitialized URI in batch RPC requests

4526d21 Add test for multiwallet batch RPC calls (Russell Yanofsky)
74182f2 Add missing batch rpc calls to python coverage logs (Russell Yanofsky)
505530c Add missing multiwallet rpc calls to python coverage logs (Russell Yanofsky)
9f67646 Make AuthServiceProxy._batch method usable (Russell Yanofsky)
e02007a Limit AuthServiceProxyWrapper.__getattr__ wrapping (Russell Yanofsky)
edafc71 Fix uninitialized URI in batch RPC requests (Russell Yanofsky)

Pull request description:

  This fixes "Wallet file not specified" errors when making batch wallet RPC calls with more than one wallet loaded. This issue was reported by @NicolasDorier in https://github.com/bitcoin/bitcoin/issues/11257

  Request URI is not used for anything except multiwallet request dispatching, so this change has no other effect.

Tree-SHA512: b3907af48a6323f864bb045ee2fa56b604188b835025ef82ba3d81673244c04228d796323cec208a676e7cd578a95ec7c7ba1e84d0158b93844d5dda8f6589b9