Improve performance of errata checking in ETT and fix fanthom nvr in errata

Remove N+1 errors

Sometimes an nvr is removed in the errata but ETT still thinks it's in the
errata. This commit also fixes that logic so that it correctly flags an nvr as
in errata or not.
Merge pull request #139 from thescouser89/nvr_in_errata_fix

Improve performance of errata checking in ETT and fix fanthom nvr in errata