Recreate test users for every test
Recreate test users for every test

The assumption currently made that "we only need to add these users
once" is only because of a hack in MediaWikiTestCase that is being
removed in If251739f.

Bug: T132411
Change-Id: I4924ae941b3844b39dd3f44c6986c3bf29b0d62a

wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo