clean up mailbox integration tests

...java/org/briarproject/bramble/mailbox/MailboxApiTest.java

...arproject/bramble/mailbox/MailboxPairingTaskImplTest.java

...va/org/briarproject/bramble/mailbox/MailboxTestUtils.java

...oject/bramble/mailbox/AbstractMailboxIntegrationTest.java

...iarproject/bramble/mailbox/MailboxApiIntegrationTest.java

...ject/bramble/mailbox/MailboxIntegrationTestComponent.java

...rproject/bramble/mailbox/MailboxIntegrationTestUtils.java

...e/mailbox/OwnMailboxContactListWorkerIntegrationTest.java

...va/org/briarproject/bramble/mailbox/TestUrlConverter.java

.../briarproject/bramble/mailbox/TestUrlConverterModule.java

...est/java/org/briarproject/bramble/test/FakeTorPlugin.java

.../briarproject/bramble/test/FakeTorPluginConfigModule.java

...a/org/briarproject/bramble/test/FakeTorPluginFactory.java