Cleanup Whitespace in unittest/ directory

Cleanup unnecessary whitespace at the end of lines and end of files
in the unittest/ directory. Note that all code changes are
non-functional.

All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer Amazon Web
Services, Inc.

unittest/sql/explain_filename-t.cc

@@ -163,4 +163,3 @@ int main(int argc __attribute__((unused)),char *argv[])
   my_end(0);
   return exit_status();
 }
-