Ensures that independent calls to `parseFilter` are isolated from one
another, by always wrapping additional clauses to the query in
`andWhere`. I think that the bug in the previous incarnation is strictly
theoretical, as long as parseFilters is only called once for a given
filter (which today, it is). When authorization lands in catalog-backend
though, we'll need to call it multiple times - once to add the authz
filters, and once to add the filters requested by the caller, which
would expose this bug.
Signed-off-by: Mike Lewis <mtlewis@users.noreply.github.com>