fix(worker): fix eq filter for non-index predicates.

[minhaj-shakeel]

Fixes DGRAPH-1781.

This PR backport the fix of eq filter on non-indexed predicate, which was fixed by #6715 earlier.

This PR fixes the eq filter for more than one argument on the non-indexed predicate which earlier used to compare with just the first of the given arguments for the eq filter. For eg for the given schema:

type CarModel {
	make
	model
	year
}
model                          : string @index(term) @lang .
make                           : string @index(term) .
year                           : int .

the below query was not giving proper results earlier.

queryCarModel(func: type(CarModel)) @filter(eq(year,2008,2009)){
				make
				model
				year
			}

---

This change is 

[OmarAyo]

Reviewed 2 of 2 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @manishrjain and @pawanrawal)

[OmarAyo]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @manishrjain and @pawanrawal)