[WIP] Pass arguments beginning with dash (-) to channel programs

[clinta]

Motivation and Context

As documented in #9056, on Linux arguments beginning with - are not send to channel programs.

Description

Prefix getopt optstring with + to force the end of option scanning after the first nonoption as documented in getopt(3).

How Has This Been Tested?

tst.args_to_lua test has been modified to use arguments beginning with - to demonstrate the issue.

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)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the ZFS on Linux code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• All commit messages are properly formatted and contain Signed-off-by.

This is a WIP first while I learn how the buildbot works and make sure the test demonstrates the bug before implementing the fix.

[behlendorf]

@clinta I'd like to close our this PR and replace it with #9428 which instead updates the documentation to require the -- separator when passing arguments to the script. Review and feedback on the documentation update would be welcome!