Disable mismerged tests committed in r362687

Reported by: lwhsu

MFC 362017, 362039, 362071:

Read commands from stdin when -f - is passed to sed(1)

This patch teaches sed to interpret a "-" in a special way when given
as an argument to the -f flag.

This behavior is also present in GNU sed.

PR: 244872
Tested by: antoine (exp-run)
Reviewed by: pfg, tobik (older version)
Approved by: pfg (src)
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D24079

Remove duplicate lines from sed tests

Reported by: yuripv
Approved by: pfg (src)

Remove some more duplicate test cases I accidentally committed

Reported by: markj, yuripv

MFC r338375:
sed: Fix -i option behavior with 'q' command.

PR: 230507

MFC r312521,r313397:

r312521:

Add testcases for -i with hardlinks and symlinks

The symlink testcase is expected to fail, post-r312519 (the revert of
r312404); mark it so.

r313397:

Don't expect :inplace_symlink_src to fail anymore (post-r313277)

The S_ISREG check was restored, such that the code will again fail with
in-place replacements on symlinks