fix(rpc): ignore non-standard "jsonrpc = 1.0" in lightwalletd requests

[teor2345]

Motivation

lightwalletd sends a "jsonrpc: 1.0" field in its RPC requests. But this field was only added in JSON-RPC 2.0, so jsonrpc_core rejects it.

Specifications

jsonrpc field:
http://www.simple-is-better.org/rpc/#differences-between-1-0-and-2-0

Valid jsonrpc_core versions:
https://docs.rs/jsonrpc-core/18.0.0/jsonrpc_core/types/request/struct.MethodCall.html#structfield.jsonrpc
https://docs.rs/jsonrpc-core/18.0.0/jsonrpc_core/types/version/enum.Version.html

Solution

• delete the non-standard fields before parsing the request

Based on ZcashFoundation#3589

Review

I'd like both @oxarbitrage and @jvff to have a look at this fix.

This fix doesn't have tests yet, but I've tested it manually.

Reviewer Checklist

• Code implements Specs and Designs
• Tests for Expected Behaviour
• Tests for Errors

Follow Up Work

• add tests with a lightwalletd instance

[codecov-commenter]

Codecov Report

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[teor2345]

The Windows failure is unrelated, it seems to be a port conflict on port 57775.
(We expect these to happen sometimes in the tests.)