iotests: Enable more tests in the 'auto' group to improve test coverage

iotests: Enable more tests in the 'auto' group to improve test coverage

According to Kevin, tests 030, 040 and 041 are among the most valuable
tests that we have, so we should always run them if possible, even if
they take a little bit longer.

According to Max, it would be good to have a test for iothreads and
migration. 127 and 256 seem to be good candidates for iothreads. For
migration, let's enable 181 and 203 (which also tests iothreads).
(091 would be a good candidate for migration, too, but Alex Bennée
reported that this test fails on ZFS file systems, so it can't be
included yet)

Reviewed-by: Max Reitz <[email protected]>
Signed-off-by: Thomas Huth <[email protected]>
Message-id: 20200121095205[email protected]
Signed-off-by: Max Reitz <[email protected]>