worker_resolve: truly honor the options parameter

It was being overwritten by options from struct kr_context;
now the flags are combined (by set union).

For example, the NO_CACHE flag is important for the prefetch module and
for trust anchor updates.
3 jobs for fix-worker_resolve-options in 3 minutes and 43 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #5272
docker linux amd64
build:linux:amd64

00:01:02

 
  Test
passed #5274
docker linux amd64
deckard:linux:amd64

00:02:41

passed #5273
docker linux amd64
test:linux:amd64

00:02:22