ZTS: test drop maybe fail exception

[behlendorf]

Motivation and Context

Try and determine which of these exceptions can be removed. Quite a lot has changed since some of these tests were disabled.

NOTE: This PR is not intended to be merged.

Description

Over the years we've identified a set of tests which aren't entirely reliable and occasionally fail. To avoid false positive CI failures we tolerate these tests occasionally failing. However, it's been a while since the list was review so as an experiment this commit drops those exceptions so we can reassess the observed failures.

How Has This Been Tested?

My intent is to run this through the CI multiple times to get a handle on which failures are still common.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Quality assurance (non-breaking change which makes the code more robust against bugs)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)