mimeview tests: make it possible to run the trac.mimeview.tests.api tests in isolation.
mimeview tests: make it possible to run the trac.mimeview.tests.api tests in isolation.

When run as part of the whole test suite, the `Converter[123]` components had the name `trac.mimeview.tests.api.converter[123]`, so they got enabled thanks to having the `trac.` prefix. When run directly, they had the name `__main__.converter[123]`, so they were not enabled, and `converters` extension point returned an empty list.


git-svn-id: 0d96b0c1a6983ccc08b3732614f4d6bfcf9cbb42@9302 af82e41b-90c4-0310-8c96-b1721e28e2e2

rbaumg/trac,rbaumg/trac,rbaumg/trac,rbaumg/trac