Pull-Request: Fix checkpwd and val in eq func in custom dql

[Schartey]

I have created a pull request for both issues. It would be nice if this could make it into the next release as it is a minor change.

https://github.com/dgraph-io/dgraph/pull/8103

while we are at it, I would like to hint at this pull-request. As firebase user this would help a lot and is also a minor change