Doesn't Work With Namespaced Datastores

[bonedaddy]

Wrapping the datastore in a namespace wrapper causes Queries to fail, as per the following output from using go-ds-bbolt with krab

=== RUN   TestKrab
--- FAIL: TestKrab (0.15s)
panic: expected prefix not found [recovered]
        panic: expected prefix not found

goroutine 21 [running]:
testing.tRunner.func1(0xc000152100)
        /usr/local/go/src/testing/testing.go:830 +0x69d
panic(0xa84fc0, 0xd03640)
        /usr/local/go/src/runtime/panic.go:522 +0x1b5
github.com/ipfs/go-datastore/keytransform.PrefixTransform.InvertKey(0xb2cfd1, 0xd, 0xc00016c0a0, 0x97, 0x0, 0x0)
        /home/solidity/go/pkg/mod/github.com/ipfs/[email protected]/keytransform/transforms.go:42 +0x229
github.com/ipfs/go-datastore/keytransform.(*Datastore).Query.func1(0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /home/solidity/go/pkg/mod/github.com/ipfs/[email protected]/keytransform/keytransform.go:78 +0x16c
github.com/ipfs/go-datastore/query.(*resultsIter).NextSync(0xc0000ecaf0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /home/solidity/go/pkg/mod/github.com/ipfs/[email protected]/query/query.go:319 +0xd4
github.com/ipfs/go-datastore/query.(*resultsIter).Rest(0xc0000ecaf0, 0x1, 0x1, 0x0, 0x0, 0x0)
        /home/solidity/go/pkg/mod/github.com/ipfs/[email protected]/query/query.go:330 +0x7f
github.com/RTradeLtd/krab.(*Keystore).List(0xc0000b8ae0, 0xb33011, 0x19, 0xd17180, 0xc0000b8e00, 0x0)
        /home/solidity/Code/krab/krab.go:107 +0x149
github.com/RTradeLtd/krab_test.TestKrab(0xc000152100)
        /home/solidity/Code/krab/krab_test.go:62 +0x4ac
testing.tRunner(0xc000152100, 0xc67f38)
        /usr/local/go/src/testing/testing.go:865 +0x164
created by testing.(*T).Run
        /usr/local/go/src/testing/testing.go:916 +0x65b
FAIL    github.com/RTradeLtd/krab       0.166s