- Fix unittest valgrind false positive uninitialised value report,

- Fix unittest valgrind false positive uninitialised value report,
  where if gcc 9.1.1 uses -O2 (but not -O1) then valgrind 3.15.0
  issues an uninitialised value for the token buffer at the str2wire.c
  rrinternal_get_owner() strcmp with the '@' value.  Rewritten to use
  straight character comparisons removes the false positive.  Also
  valgrinds --expensive-definedness-checks=yes can stop this false
  positive.