Fix multiwallet to use `self.assert_start_raises_init_error`
Fix multiwallet to use `self.assert_start_raises_init_error`

Summary:
Multiwallet was using the incorrect `assert_start_raises_init_error`
due to a diff ordering issue when landing.

Fixes T195

Test Plan: `make && test/functional/test_runner.py multitest`

Reviewers: deadalnix, matiu, jasonbcox, #bitcoin_abc

Reviewed By: deadalnix, #bitcoin_abc

Subscribers: teamcity

Maniphest Tasks: T195

Differential Revision: https://reviews.bitcoinabc.org/D1025

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