Rather than using the dnspython's facilities and defaults to create the
queries, use the isctest.query.create function in all the cases that
don't require special handling to have consistent defaults.
The old name "common" clashes with the convention of system test
directory naming. It appears as a system test directory, but it only
contains helper files.
To reduce confusion and to allow automatic detection of issues with
possibly missing test files, rename the helper directory to "_common".
The leading underscore indicates the directory is different and the its
name can no longer be confused with regular system test directories.
