Minor test suite modifications

[james-bruten-mo]

Minor modifications to some files for use in the test suite.

• Modify the error message in umdp3_fixer to point to new location of this script
• Remove references to fcm_bdiff from copyright_checker. These aren't replaced with git_bdiff as they are never actually used in the test suites.
• Remove the rose_orig_host line from the trac.log
• Set the default branch to "main" for all repos

I think 1 level of review is fine for these changes.